Thank you to Hoskins. Definitions are underlined in the clues.
Across
1. Conservative and liberal creep in embrace (6)
CLINCH : C(abbrev. for a member of the Conservative Party) plus(and) L(abbrev. for a member of the Liberal Party) + INCH(to creep/to move along slowly and carefully).
4. Alpha female snorts coke of high quality (3-5)
TOP-CLASS : [ TOP LASS ](term for the dominant female in a group – the counterpart of the alpha male) containing(snorts) C(abbrev. for “coke”/cocaine).
10. Modern fortified building in English city (9)
NEWCASTLE : NEW(modern/up to date) + CASTLE(a fortified building/fortress).
11. Best party, getting gone in the head! (5)
OUTDO : DO(a party/a social function) placed after(getting … in the head) OUT(gone/not present).
Defn: To …/surpass.
12. Story with knight stealing new bedding? (5)
LINEN : LIE(a story/untruth) plus(with) N(symbol for “knight” in chess notation) containing(stealing) N(abbrev. for “new”).
13. A vocal on Substitute or Out of Time? (9)
ATEMPORAL : A + [ ORAL(vocal/spoken) placed after(on) TEMP(a person employed as a substitute for a regular employee who is away) ].
Defn: …/free from the influence or constraints of time.
And, of course, “Substitute” by The Who, “Substitute” by the Righteous Brothers, and later by Clout, and “Out of Time” by the Rolling Stones and covered by Chris Farlowe, are songs with vocals.
14. Unfeeling member very posh girl rejected (4,3)
DEAD LEG : DEAD(very/absolutely, as in “you’re dead wrong about that”) + reversal of(… rejected) GEL(an informal term for a posh/upper-class girl).
Answer: A member of the body, specifically a lower limb, that has gone numb/unfeeling after injury.
16. French main? Opening unopened wine! (6)
MERLOT : MER(French for “sea”/the main) + “slot”(a narrow elongated opening) minus its 1st letter(unopened).
Defn: A red ….
18. Hoskins is dim prick all the way through! (6)
IMPALE : I’M(I am/Hoskins is, using the self-referential pronoun) + PALE(dim/lacking brightness).
Did I hear someone say: “You’re wrong … he’s not dim!” 😀
20. Londoner likely to knock Hoskins’s head off? (7)
COCKNEY : Cryptic defn: A London native who is likely to drop/knock off the 1st letter/head when pronouncing “Hoskins”.
23. One who legs it if Rob dances badly (9)
ABSCONDER : Anagram of(… badly) ROB DANCES.
Defn: …/goes away suddenly to escape from a place.
25. Sleep for short while with old man in leather (5)
NAPPA : NAP(to sleep for a short while/take 40 winks) plus(with) PA(like “old man”, a familiar term for one’s father).
Leather of choice:

27. Sinful things produced by out-of-head fiends (5)
EVILS : 1st letter deleted from(out-of-head) “devils”(fiends/wicked persons).
28. Drinking booze? So then sip to get drunk! (2,3,4)
ON THE PISS : Anagram of(… to get drunk) SO THEN SIP.
Defn: Slang for …/alcohol in large quantities.
29. Girl eyed criminal in a rapacious way (8)
GREEDILY : Anagram of(… criminal) GIRL EYED.
30. A northern set with southern backers (6)
ANGELS : A + N(abbrev. for “northern”) + GEL(to set/to become more solid) + S(abbrev. for “southern”).
Defn: Financial … of businesses.
Down
1. Wind up Tory with hint about dire leader (8)
CONCLUDE : CON(abbrev. for a member of the Conservative Party/a Tory) plus(with) CLUE(a hint/a pointer to the solution to a problem) containing(about) 1st letter of(… leader) “dire“.
Defn: …/to bring to a close.
2. I love pasty-looking chap in a state, perhaps (5)
IOWAN : I + O(letter representing 0/love in tennis scores) + WAN(pasty-looking/lacking colour).
Defn: Chap from one of the US states, in this case/perhaps, Iowa.
For example:

3. Perfume manufacturer getting in new groove? (7)
CHANNEL : CHANEL(Coco, French perfumer and the company she founded) containing(getting in) N(abbrev. for “new”).
5. Old worker snarfing seconds could be thus (5)
OBESE : O(abbrev. for “old”) + BEE(a member of any of the family of social insects, one caste of which is the worker) containing(snarfing) S(abbrev. for “seconds” in time notation).
Defn: …, ie. overweight after greedily eating/snarfing second helpings.
6. Policeman injecting horse will get the axe (7)
CHOPPER : COPPER(informal term for a policeman) containing(injecting) H(abbrev. for “horse”/heroin).
7. No one fart about when Hoskins gets up! (9)
AFTERNOON : Anagram of(… about) NO ONE FART.
Defn: Time of the day …, if you can believe it!
8. Overindulges and goes off booty (6)
SPOILS : Triple defn: 1st: …/pampers; 2nd: …/becomes unfit for eating; and 3: …/valuable stolen goods.
9. Unusual to grab head of lizard and choke (8)
STRANGLE : STRANGE(unusual/odd) containing(to grab) 1st letter of(head of) “lizard“.
15. It’s a crime to break peaceful agreement (9)
ARMISTICE : Anagram of(… to break) IT’S A CRIME.
16. Thin Frenchman with brilliant speed (8)
MACERATE : M(abbrev. for “Monsieur”, term of address for a Frenchman) plus(with) ACE(brilliant/excellent) + RATE(speed/pace).
Defn: To …/cause to waste away.
17. Ring roads close to old-fashioned school (8)
BYPASSES : BY(close/next to) + PASSÉ(old-fashioned/out of date) + S(abbrev. for “school”).
19. A wine opened by old American gets you excited (7)
AROUSED : A + [ RED(a red wine) containing(opened by) [ O(abbrev. for “old”) + US(abbrev. for “United States”, describing things American) ].
21. Is it possible that adolescent is a mess? (7)
CANTEEN : CAN?(is it possible that …?) + TEEN(short for “teenager”/an adolescent).
Defn: A place where meals are served and eaten – called a mess if it is for the armed forces.
22. Dodgy bloke, one Edwina worried about? (3,3)
BAD EGG : Cryptic defn: Reference to the UK Parliamentary Under-Secretary of State for Health, Edwina Currie warning the public about salmonella in eggs in 1988.
24. Leader of DUP having sex is quaintly comical (5)
DROLL : 1st letter of(Leader of) “DUP” plus(having) ROLL(slang for sexual intercourse, as in “a roll in the hay”).
26. Vacuous police surrounding free festival (5)
PRIDE : Inner letters deleted from(Vacuous) “police” containing(surrounding) RID(to free/remove from).
Defn: …/public event, in this case, to celebrate LGBT identities, culture and experience.

COTD: COCKNEY
Also liked ON THE PISS (nice surface) and the funny AFTERNOON.
Enjoyable puzzle. Thanks Hoskins.
Great blog. Thanks scchua.
I could hear Roger Daltry and Chris Marlowe singing those songs as clearly as if it was yesterday. Is that an ATEMPORAL experience? Took a while to solve that clue though. Lovely Sunday puzzle and blog with pictures Thanks scchua and Hoskins.
But I forgot to spell his name correctly. Farlowe. Sorry, Chris.
At 20A, I briefly wondered whether there was an underlying reference to David ‘Ockney, but probably not! Much enjoyed anyway, so thanks ‘Oskins and Scchua
Excellent. Hoskins at his most irreverent with too many good clues to list them all.
Many thanks to Harry and to scchua.
CONCLUDE/dire leader very good. Especially after last Thursday.
For all the stick Hoskins has had I’d prefer ribaldry to reminders of the bad eggs woman.
Thanks Hoskins and scchua.
I agree RD.
As soon as I saw it was ‘oskins I prepared my mental checklist
Sex, yes and Edwina!
Drugs, yes coke and horse
Rock and roll, yes I look pretty young but I’m just backdated.
Booze, yes of course
Bodily functions, yes naturally.
I think that’s the full set
Thanks to setter and blogger.
Great stuff
Thanks to setter for a good puzzle, and blogger for
All good.. I’d forgotten how well I remembered Edwina n the eggs!! I do enjoy the full use of available language without diving into the totally obscure.. always refreshing, Hoskins keeping it real.. if I had to pick one it would be18ac.
Thanks Hoskins n scchua
Our ‘arry at his irreverent best – strange how he manages to get away with it where other setters simply haven’t got the knack. Impossible to pick just one favourite, I laughed all the way through the solve.
Many thanks to the afternooner and to scchua for the review.
I can’t put it better than Jane. 18A 20A combo? Classic!