Thank you to Hoskins. Definitions are underlined in the clues.
Across
6. Take Scottish leader’s temperature for doc (7)
SURGEON : “T”(symbol for “temperature” in physics) deleted from(Take) “Sturgeon”(Nicola, First Minister of Scotland).
Defn: …/doctor, specifically one practising surgery.
7. Love a revolutionary being ready for a row? (5)
OARED : O(letter representing 0/love in tennis scores) + A + RED(a revolutionary/one who advocates the violent overthrow of an existing social or political order).
Defn: … in a rowing boat.
9. Old relative managed after touch of gout (4)
GRAN : RAN(managed, say, an organisation) placed after(after) 1st letter of(touch of) “gout“.
10. Part of the body pervert has up goose (10)
OESOPHAGUS : Anagram of(pervert) HAS UP GOOSE.
11. Quiet passes could be deciding matches (4-4)
PLAY-OFFS : P(abbrev. for “piano”, the musical direction to play softly/quietly) + LAY OFFS(in soccer, passes to a team mate to gain advantage).
13. Hot member close to tears and ready to fight (2,4)
IN ARMS : IN(hot/currently popular) + ARM(one of one’s members/limbs) + last letter of(close to) “tears“.
15. Afternoon out for country drive (4)
SPIN : “A”(abbrev. for “afternoon”, as in “ga/good afternoon” – admittedly not as common as “pm”) deleted from(out) “Spain”, the European country.
Defn: … – a short one in a vehicle for pleasure.
17. I will wear medal in retirement (5)
GOING : I contained in(will wear) GONG(slang for a medal or award).
Defn: The act of retiring/leaving one’s job and ceasing to work.
Answer: …, as a noun.
18. Fat landowner that’s repelled one (4)
LARD : “laird”(a Scottish landowner) minus(that’s repelled) “I”(Roman numeral for “one”).
19. Some soothing rap pacifies spirit (6)
GRAPPA : Hidden in(Some) “soothing rap pacifies“.
Defn: …/a brandy made from fermented grapes which have already been pressed for winemaking.
20. Hats and clothes for a principal? (8)
HEADGEAR : GEAR(clothes) placed after(for) HEAD(a principal/the most important person in a group) – similar in construction to “adult entertainment”
23. Don’t scream after a shock in Boots (3,7)
DOC MARTENS : Anagram of(… after a shock) DON’T SCREAM.
Defn: …/branded footwear from the Dr. Martens Company.
26. Kid in sound or river (4)
TEES : Homophone of(… in sound) “tease”(to kid/to make fun of).
Defn: … in northern England.
27. Who cares if second husband gets wig? (5)
SHRUG : S(abbrev. for “second” in time notation) + H(abbrev. for “husband”) plus(gets) RUG(slang for a wig).
Defn: … gesture expressing “Who cares? I don’t.”
28. Ready for a spanking? Mind your own business! (4,3)
BUTT OUT : Cryptic defn: Reference to the posture – bending down so that your rear end/butt sticks out – adopted in readiness for a spanking on the buttocks.
Down
1. Bishop up for sex and crack takes the biscuit! (6,4)
BRANDY SNAP : B(abbrev. for “bishop” in chess notation) + RANDY(up/ever ready for sex/horny) plus(and) SNAP!(crack/a sudden sharp noise).
2. In Paris, the aristocrat gets reprieve (3,3)
LET OFF : LE(the grammatical article “the”, in the language of Paris, France) + TOFF(an aristocrat/an upper-class person).
3. Out-of-head Scandinavians and boozers … (4)
INNS : 1st letter deleted from(Out-of-head) “Finns”(the people of Finland, part of “Scandinavia”, used broadly).
4. … hooking up and having sex (8)
COUPLING : Double defn: 1st: … as in, say, the horse to the cart; and 2nd: As with a pair …
5. Song artist sent up by flipping smart software? (4)
ARIA : Reversal of(… sent up, in a down clue) RA(a member of the Royal Academy of Arts/an artist) plus(by) reversal of(flipping) AI(abbrev. for “artificial intelligence”/smart software intended to emulate human and animal intelligence).
6. French thinker annoyed Hegel ultimately (5)
SOREL : SORE(annoyed/upset and angry) + last letter of(… ultimately) “Hegel“.
Answer: …, Georges, thinker/philosopher.
And Hegel was an earlier German philosopher.
8. One prone to beat male involved in sick murder (7)
DRUMMER : M(abbrev. for “male”) contained in(involved in) anagram of(sick) MURDER.
One not only prone to, but damn good at it:
12. Small desire or fancy (5)
SWISH : S(abbrev. for “small”) + WISH(a wish/what one would like to have).
Defn: …/fashionable and impressive-looking.
14. A long tale I edited (for a charge) (10)
ALLEGATION : Anagram of(… edited) A LONG TALE I.
Defn: …/an accusation.
16. Normal lads could become folk of the clergy (7)
PARSONS : PAR(normal/standard, as in “par for the course”) + SONS(a term one uses for boys/lads, even if they not related to one).
Defn: …/members of the cloth.
17. Good boy with kids in Sunday dress? (4,4)
GLAD RAGS : G(abbrev. for “good”) + LAD(a young boy) plus(with) RAGS(kids/teases).
From Sunday church: 
to graduation ball: 
21. Idiots grabbing tyrannical leader’s family jewels? (6)
ASSETS : ASSES(idiots/stupid persons) containing(grabbing) 1st letter of(… leader) “tyrannical“.
Defn: An example of which/? would be …
22. A time to hide dope plant? (5)
AGENT : [A + T(abbrev. for “time”)] containing(to hide) GEN(dope/information).
Defn: …/one placed/planted in a group as a spy or informer/a secret agent.
24. Extra foreign capital, exchanging Rupees and Marks (4)
MORE : ROME(the capital city, foreign if you’re not Italian) with “R”(abbrev. for Rupees) and M(abbrev. for “Marks”) switching places(exchanging).
25. In good shape, after going up rocky island (4)
ELBA : Reversal of… after going up, in a down clue) ABLE(in good shape/having the requirements to achieve something).
A few of the expected racy Hoskins surfaces made this a fun solve. There were some I couldn’t parse, so thanks for explaining SPIN which I never would have worked out. The ‘French thinker’ was also new, a bit surprising given what Wikipedia explains was his influence on Marxism.
Good to see an anagram of ‘murder’ (yes, OK with one more letter) not referring to a certain racehorse and I enjoyed your associated YouTube clip.
Thanks to scchua and to Hoskins
A quick but fun solve. Didn’t know that meaning for “lay off” in 11a and only vaguely remember seeing a for afternoon before (bit like s for saint). SOREL was also new for me. My favourite was the outrageous clue for OESOPHAGUS. Thanks to Hoskins and scchua (strange seeing a drummer in evening wear).
I thought the definition for 17a was a bit dodgy but other than that this was great fun from Hoskins as usual. PLAY-OFFS was my favourite.
Many thanks to Hoskins and to scchua.
Lovely stuff.
Favourite was Doc Martens.
LOI tees, after staring at teen for way too long.
Well, I thought 15A a bit dodgy even after Scchua’s explanation. Can ‘m’ also be used for ‘morning’? I struggled in the SE corner but eventually solved ‘butt out’, although never heard that expression before for ‘mind your own business’. Thanks Hoskins for the amusement and Scchua for the entertaining blog.
Thanks to Hoskins for a lorra laffs; perhaps even more than usual today. Great stuff – DOC MARTENS, OESOPHAGUS, BUTT OUT and even a sneaky little LET OFF. Jane will be giving this one a swerve, I imagine. I wondered if IN ARMS on its own - without the up – is kosher but I guess it must be.
Thanks to scchua for the blog (have you changed your font settings? – I needed to get my specs on)
Nice to see a few flashes of the ‘old’ Harry in this one and a relief to discover that I wasn’t alone in not knowing the football term or the French thinker.
Quite a lot of ticks on my sheet – SHRUG, BUTT OUT, LET OFF & GLAD RAGS all getting a mention.
Thanks to Hoskins and also to scchua for the review.
Baerchen@6 – your comment must have popped up whilst I was typing. No complaints from me today!
@ Tatarasman #5 I don’t think M for morning would be acceptable but A for Afternoon (or vice versa is because Chambers has it as one of the meanings for A. I don’t know anyone who’s ever used AB to refer to a sailor anywhere other than in a crossword but we accept it (or at least I do) because Chambers has it and we’ve got used to it!
Hi Bluth. Where would we be in these Covid times without scatology? No Bluth, Hoskins, Phi, Paul aka Mudd etc. And stimulant without smut!