Across:
1 Geronimo (Geronimo! = WAR CRY) circumspect (WA-RY) over religion (Roman Catholic = -R C-) (WAR CRY),
4 Drag (tow) up (= reversal indicator) (tow = -WO-T-) in magazine (Time magazine = T-IME) bad ending (‘baD’ ending = -D) (TWO-TIMED) to what cheat did to lover (TWO-TIMED),
9 Foolish figure (ASS-) gets very good marks at university (1st = -IST) (ASSIST) with help (ASSIST),
10 21 across (‘wards’ = WARDS-) gets joint (-HIP joint) (WARDSHIP) custody (WARDSHIP),
12 Influence (DOMINANCE) of funny (= anagram indicator) comedian (comedian = DOMINA-CE) over One Direction (North = -N-) (DOMINANCE),
13 Some material air support (some ‘materiaL AIR Support’ = LAIRS) for those living in secret (LAIRS),
14 Half of those in 27 across (half of ‘WARmed’ = WAR-) from England (-E-) not operating long in a hospital (junior doctor = -HOUSEMAN) (WAREHOUSEMAN) or working in storage facility (WAREHOUSEMAN),
18 Promoting serious confrontation (WARMONGERING) by starting 1 across (starting ‘war cry’ = WAR) with broadcast (-ON-) occupying Meg (Meg) Rock (= anagram indicator) (Meg = M-GE-) in Waterford (-RING) (WARMONGERING),
21 Sets up (= reverse indicator) inexperienced (raw = WAR-) detective (DS = -DS) (WARDS) for charges (WARDS),
22 Your close contacts (NEXT OF KIN) at the end of 5 down? (the end of ‘whatever next’ = NEXT) That’s fine by me (O- K-) getting to grips with frequency (-F) at home! (-IN) (NEXT OF KIN),
24 Patrick (-PAT-) and Henry (-H-) consumed by the Little Piggies (toes) heard (= homophone indicator) (‘toes’ = ‘tows’ = TOW-S) (TOWPATHS) going along the canals (TOWPATHS),
25 They save the day (HEROES) for that woman (HER-) from The Opposition (foes) losing the head (f) (‘foes’ without ‘f’ = -OES) (HEROES),
26 It’s not easy (HARD-) to spot (spot) review (= reverse indicator) (spot = -TOPS) (HARDTOPS) of cars that give the impression they could be convertibles (HARDTOPS),
27 What The Sun did perhaps (what the sun did = WARMED) for women (W-) taking piece (piece/arm = -ARM-) to editor? (-ED) (WARMED).
Down:
1 Gradually tire (WEAR DOWN) of sport (sport/display = WEAR) in Ulster (DOWN) (WEAR DOWN),
2 Two women married (Rose + Mary = ROSEMARY) to Herb? (herb = ROSEMARY),
3 It’s about (RE-) what’s not right (-SIN) (RESIN) in various plants and trees (RESIN),
5 Who cares (WHATEVER) what the cashier says (NEXT) (WHATEVER NEXT), as it comes as a surprise (WHATEVER NEXT),
6 The overwhelming emotion (TIDAL WAVE) produced by politician (TD = T-D-) welcoming one (-I-) gangster (-AL Capone) on white horse (white horse/white-crested WAVE) (TIDAL WAVE),
7 Fleece (MOHAIR) some of the characters caught up (= reverse indicator) in Umbria homicide (some of the characters in ‘umbRIA HOMicide’ = riahom = MOHAIR),
8 Remove from The Office (DEPOSE), as is not in the episodes? (‘is’ not in the ‘episodes’ = epodes = DEPOSE),
11 Individual (ONE-) going to a wake (‘a wake’ = ‘awake’ = -UP-) for worker (-MAN-) on boat (-SHIP) (ONE-UPMANSHIP) is showing up a rival (ONE-UPMANSHIP),
15 The nod (HEAD START) from principal (HEAD) for a local job (local ‘job’ = a START) (HEAD START),
16 Boss (= anagram indicator) milks row (milks row = SILKWORM) with one of those cocooning, in the material sense (SILKWORM spins a silk cocoon),
17 Worried about (AGONISED) sea dog in (sea dog in) trouble (= anagram indicator) (sea dog in = AGONISED),
19 Barman (Senior Counsel/SC = S-C-) protects funny fellow (-WIT-) from hotel (-H) (SWITCH) getting on (SWITCH),
20 One of those supplying the pictures (DRAWER) in The Press (DRAWER is in the press),
23 Old (O-) country (Peru) reduced (u) (‘Peru’ without ‘u’ = PER-) area (-A) (OPERA) for Bluebeard’s Castle, for example (Béla Bartók’s ‘Bluebeard’s Castle’ = OPERA).