Across:
1 Heard (= homophone indicator) luck (‘luck’ = ‘look’ = SEE-) was (was) turning (= reversal indicator) (was = -SAW) (SEESAW), as it can be up and down (SEESAW),
4 Make it less of a challenge (DUMB DOWN) for male (-M-) taken in by woman from the capital (DUB = DU-B) in Northern Ireland (DOWN) (DUMB DOWN),
9 Review of (= reverse indicator) El Cid (El Cid) clip (d) (‘El Cid’ without ‘d’ = elci = -ICLE) starts with cinematic intensity (starts with ‘Cinematic Intensity’ = CI = IC-) (ICICLE) of one hanging outside in the cold (ICICLE),
10 Turns up (= reverse indicator), the foreign (the = el = -LE) graduate (BA = -AB-) at bar (rod = -DOR-) is (A-) (ADORABLE) a precious type (ADORABLE),
12 Club official (TREASURER) responsible for 26 across perhaps (TREASURER responsible for ‘treasury’ perhaps),
13 Experience hallucinations (TRIP-) on drug (-E) (TRIPE) locally? That’s nonsense! (‘local’ nonsense = TRIPE),
14 It’s not a disaster (SUCCESS STORY) to say I did it (SUCCESS!) with novel idea (STORY) (SUCCESS STORY),
18 The very best (SECOND TO NONE) in 25 across (‘second’ = SECOND) gets 2,240 pounds (2,240 pounds = ton = TO N-) from individual? (one = -ONE) (SECOND TO NONE),
21 Pick up (HEAR-) car (model T = -T) (HEART) with enthusiasm (HEART),
22 Unsecured type (FREE) on water (DRINK) (FREE DRINK) by port costing nothing (FREE DRINK),
24 Has natural ability (INSTINCT) to nose? (INSTINCT),
25 Absconders removed bars (‘absconders’ removed ‘bars’ = sconde = SECOND) in the briefest of times (SECOND),
26 Estuary (Estuary = T-EASURY) flowing (= anagram indicator) around river (-R-) (TREASURY) bank (TREASURY),
27 Finishes the lot (USES UP) and takes drugs (USES) to stay awake (UP) (USES UP).
Down:
1 Local has no money (‘local’ skint = SKIN T-) to set (set) in motion (= anagram indicator) (set = -EST) (SKIN TEST) a medical check for allergy (SKIN TEST),
2 Proof (EVIDENCE) of vice-president not taking trips (‘vice-president’ not taking ‘trips’ = viceeden = EVIDENCE),
3 At the least, remove teeth (‘at the least’ remove ‘teeth’= alast = ATLAS) of legendary strongman (ATLAS),
5 Works in the abbey occasionally (works in The Abbey Theatre occasionally = UNDERSTUDIES) beneath (UNDER) writing rooms (-STUDIES) (UNDERSTUDIES),
6 What one tends to see when someone loses their shirt (BARE TORSO) in pub (BAR-) taking ecstasy (-E) with sculptured figure (TORSO) (BARE TORSO),
7 Awaiting trial (ON BAIL) to play (= anagram indicator) Albion? (Albion = ON BAIL),
8 Makes (= anagram indicator) scene (scene = N-ECES) over one (-I-) (NIECES) lot of relatives (NIECES),
11 One of those selling story to the media (PRESS OFFICER) has crush (PRESS) on company man? (OFFICER in company/ army) (PRESS OFFICER),
15 Vote in (ELECT-) old police (Royal Irish Constabulary = -RIC-) station introducing (‘Station’ introducing = -S) (ELECTRICS) those synonymous with The Wire (ELECTRICS),
16 The Observer’s (MONITORS) leaders modelled on (leaders ‘Modelled On’ = MO-) adapted (= anagram indicator) intros (intros = -NITORS) (MONITORS),
17 Sweetheart (‘swEet’ heart = -E-) behind (= position indicator) benefit (PERK-) party (Democratic Unionist Party = DUP = -D UP) (PERKED UP) suddenly got excited (PERKED UP),
19 Prudence (THRIFT) and Regina getting off freight train (‘Regina’ getting off ‘freight train’ = fhttri = THRIFT),
20 Harry (HASSLE) lashes (lashes) out (= anagram indicator) (lashes = HASSLE),
23 Unfair to leave fundraisers (‘unfair’ to leave ‘fundraisers’ = dsers = DRESS) in Mini (mini DRESS).