Across:
8 Some secret I regret (some ‘secret I regret’ = RETIRE) of how to give up work (RETIRE),
9 On approach to clubhouse, for instance (DRIVEWAY), hit the ball (DRIVE- the golf ball) with technique (-WAY) (DRIVEWAY),
10 Patriotism lacks spirit (‘patriotism’ lacks ‘spirit’ = atom = ATOM), a little bit (ATOM),
11 Type of drink (MINERAL) from Greece (‘Greece’ = ‘grease’ = OIL) – on the tongue (= homophone indicator) (MINERAL OIL) it’s a very refined, clear liquid for the constipated (MINERAL OIL),
12 Shutdown (SEALED) a Leeds (a Leeds = SEALED) production (= anagram indicator),
14 Caught (-C-) in colliery (MIN-E) by detective (PI-) with ecstasy (-E) (MINCE PIE) produced for the Christmas market (MINCE PIE),
15 Whistling in the galley (whistling in the galley/kettle boiling in the galley kitchen = LETTNG OFF STEAM) is releasing the tension (LETTNG OFF STEAM),
18 Little gems (examples of LETTUCES) from rough- (= anagram indicator) -cut steel (cut steel = LETTUCES),
20 Last letters (-RIP-) covered up in a French article (French ‘a’ = une = UN-E) (UNRIPE) not fit for consumption (UNRIPE),
22 Nonsense (BULL) from defensive opponent (marker) clipped (r) (‘marker’ without ‘r’ = MARKE-) and tripped initially (‘tripped’ initially = -T) (BULL MARKET) by one whose stock is on the rise (Stock Exchange BULL MARKET),
24 Have the effrontery (DARE) to serve up (= reversal indicator) bit of horseradish (bit of ‘horseradish’ = erad = DARE),
25 Vetted an (vetted an = VENDETTA) organisation (= anagram indicator) for bad blood (VENDETTA),
26 No menace in trace element (no ‘menace’ in ‘trace element’ = trelet = LETTER) that came in the post (LETTER).
Down:
1 Sympathetic (GENTLE) to sides generous to Newcastle (to sides ‘generous to Newcastle’ = GENTLE),
2 Irish men (Irish ‘men’ = FIR-) married (-M) (FIRM) to the job (FIRM),
3 British (B-) bird (emu = E-MU-) admits reading (-R-) abridged version (e) of Hamlet (‘Dane’ without ‘e’ = -DAN-) (BERMUDAN) to an islander living in a place known for its disappearances (living in Bermuda Triangle = BERMUDAN),
4 Some revolutionary (= reversal indicator) aubergine developed (some ‘aubergine developed’ = nede = EDEN) for the gardeners initially (EDEN),
5 Splash (= anagram indicator) tonic (tonic = CIT-ON) over recipe (-R-) (CITRON) for making lemonade (CITRON),
6 Head on foxglove (head on ‘foxglove’ = F-) flower (flower/River Lee) coming up (= reversal indicator) (Lee = -EEL) is in a different class (BETTER) (FEEL BETTER) to improve (FEEL BETTER),
7 Bails (bails = BASIL-) out (= anagram indicator) women’s institute (Irish Countrywomen’s Association = -ICA) (BASILICA) for having a word with the man upstairs (BASILICA),
13 Don’t mention (LET IT SLIDE) the French (the = LE-) bird (-T IT) spotted in children’s playground (SLIDE) (LET IT SLIDE),
14 Kitchen (room = MOOR-) serves up (= reversal indicator) something for starter (‘something’ for starter = -S) (MOORS) from wastelands (MOORS),
16 Puts the plan into action (EXECUTES) for directors (executives) dismissing four from Rome (Roman four = IV) (‘executives’ without ‘iv’ = executes = EXECUTES),
17 To go hell for leather (FLY) after (= positional indicator) being in a jam (FRUIT) (FRUIT FLY) can be a pest on a date (FRUIT FLY is a pest on a date/fruit),
19 Credit (CR-) American (-A-) paper’s (Financial Times’s = FTs = -FTS) (CRAFTS) artistry and workmanship, for instance (CRAFTS),
21 Report (report = PORTER) rogue (= anagram indicator) to the one carrying baggage (PORTER),
23 Foreign hate group (Ku Klux KLAN) attack language content (‘attack language’ content = KLAN),
24 No pubs in Budapest (no ‘pubs’ in ‘Budapest’ = daet = DATE) for lovely social engagement (DATE).