Across:
1 Heal or (heal or = LAHORE) cure (= anagram indicator) in Asian city (LAHORE),
4 The bad tempered old woman (HARRIDAN) replacing (= anagram indicator) H.R.R. Diana? (HRR Diana = HARRIDAN),
9 Pulse (LENTIL) is fast (LENT-) on one (-I-) learner driver (-L) (LENTIL),
10 Agent (SPY-) finishes 12 across (‘pick a hole’ = -HOLE-) with One Direction (south = -S) (SPYHOLES) offering to keep an eye or two on The Doors (SPYHOLES),
12 Find fault (PICK A HOLE) with best (PICK) area (A) for the swingers to target (swingers/golfers target HOLE) (PICK A HOLE),
13 Part of Malaga invokes (part of ‘Malaga invokes’ = AGAIN) another time (AGAIN),
14 Selling property (DAFT property website) to a (-A-) South African (-S A) bishop (B-) in north Dublin (-RUSH) (DAFT AS A BRUSH) is simple (DAFT AS A BRUSH),
18 Put away (EAT) with low-ranking type (HUMBLE) from 5 down, for example? (‘apple crumble’ = PIE) (EAT HUMBLE PIE) Make a humiliating apology! (EAT HUMBLE PIE),
21 Really big (OBESE) Fords removed from bed of roses (‘Fords’ removed from ‘bed of roses’ = beose = OBESE),
22 You’d expect to be better after this (better after ILL HEALTH) dicky (ILL) remedy (HEAL-), for the (the) most part (e) (‘the’ without ‘e’ = -TH) (ILL HEALTH),
24 It’s a ferocious struggle (DOGFIGHT) getting boxer (DOG-) to box (-FIGHT) (DOGFIGHT),
25 Turning up (= reversal indicator) nice street (Nice/French ‘street’ = ‘rue’ = -EUR) with sense of purpose, leaders (‘sense of purpose’ leaders = sop = POS-) (POSEUR) seeking attention (POSEUR),
26 The thickest (OBTUSEST) hooligan (yob) loses the head (y) (‘yob’ without ‘y’ = OB-) and takes drugs (-USES-) in race (TT race = -T-T) (OBTUSEST),
27 Take away (LESS-) drugs (-EE) (LESSEE) for someone paying a flat fee (LESSEE).
Down:
1 Bluebell relative (LILY) packs (PADS) (LILY PADS) for those going across The Pond (LILY PADS),
2 Restrain (HANDCUFF) worker (HAND-) from getting caught (-C-) by paramilitaries (Ulster Freedom Fighters = -UFF) (HANDCUFF),
3 Tailor-made without model (‘tailor-made’ without ‘model’ = taira = RAITA) for a dippy Indian type (RAITA),
5 Cider producer (APPLE) to break up (CRUMBLE) (APPLE CRUMBLE) with sweet type (APPLE CRUMBLE),
6 Attends at a recital, for instance (-HEARS-), in authentic (real = RE-AL) (REHEARSAL) practice in the abbey (REHEARSAL in The Abbey Theatre),
7 Upsets (= reversal indicator) everyone (all = -LLA-) in bar (rod = DO-R) (DOLLAR) in foreign capital (foreign capital/money = DOLLAR),
8 Slag off singalongs (‘slag’ off ‘singalongs’ = inongs = NOSING) for uncovering things belonging to others (NOSING),
11 Some people are afraid of them (afraid of HEIGHTS) after (= positional indicator) Anglo (Anglo = GOLAN) collapse (= anagram indicator) (GOLAN HEIGHTS) and, if we go there, are we going into a disputed area? (GOLAN HEIGHTS),
15 American (A-) accountant (-CA-) doctors (= anagram indicator), medics (medics = -DEMICS) (ACADEMICS) – all working in teaching institute (ACADEMICS),
16 Peter Sellers cuts tree (‘Peter Sellers’ cuts ‘tree’ = psellers = SPELLERS) for the witches perhaps (SPELLERS),
17 Archer (archer = RECHAR-) hit (= anagram indicator) middle of the battleground (middle of the ‘battleground’ = eg = -GE) setting up (= reversal indicator) (RECHARGE) attack again (RECHARGE),
19 Cover (HOOD-) made look good at the centre (‘made look good’ at the centre = -OO) (HOODOO) is a bit of devilment (HOODOO),
20 From rock bottom, goes all the way to the top (HEIGHT) with most of them at the end of 11 down (‘Golan Heights’ = HEIGHT),
23 Gradually destroy (ERODE) drugs (E+E = E-E) found on both sides of bar (bar = -ROD-) (ERODE).