Across:
1 Remedy (ANSWER) is way out? (ANSWER),
4 Farm animals (swine = SWIN-E-) roaming Donegal (-DL-) registered (-R) (SWINDLER) to one of those running a scam (SWINDLER),
9 Top (T-SHIRT) car? (model T-) Could be a Polo! (polo -SHIRT) (T-SHIRT),
10 Recover what’s due (CLAWBACK) in principle (principle/rule = -LAW-) following (= position indicator) club (C-) – that’s what any gambler would do? (-BACK) (CLAWBACK),
12 Student (UNDERGRAD) of Red Guard (red guard) corruption (= anagram indicator) (red guard = U-DERGRAD) around end of Revolution (end of ‘revolutioN’ = -N-) (UNDERGRAD),
13 Makes miserable (PAINS) secretary (Personal Assistant = PA-) popular (-IN-) at Society (-S) (PAINS),
14 One taking orders (SALESMAN-) on vessel (-SHIP) (SALESMANSHIP) selling sand to the Arabs (SALESMANSHIP),
18 Picture (SELF-PORTRAIT) what only you are capable of, you poser (SELF-PORTRAIT),
21 Collect (AMASS) those in Mount Ossa mad (those in ‘mount oSSA MAd’ = ssama) to return (= reverse indicator) (ssama = AMASS),
22 The issue new union brought up (STEPCHILD) for most of those opening 15 down (most of ‘steps down’ = STEP-) with 23 down (‘child’ = -CHILD) (STEPCHILD),
24 Wild (= anagram indicator) ostrich (ostrich = HISTOR-C) roaming around one (-I-) (HISTORIC) landmark (HISTORIC),
25 Wash one’s hands of (DISOWN) One (-I-) Direction (South = -S-) in county up north (Down = D-OWN) (DISOWN),
26 Ditch (DRAINAGE) wild (= anagram indicator) gardenia (gardenia = DRAINAGE),
27 They do nothing (IDLERS) with the loungers (IDLERS).
Down:
1 A-list rum (A-list rum) cocktail (= anagram indicator) (a-list rum = ALTRUISM) – is that a measure of public-spiritedness? (ALTRUISM),
2 Small (S-) revolutionary (-CHE-), briefly (l) boring (‘dull’ without ‘l’ = -DUL-), foundation volume (foundation ‘volumE’ = -E) (SCHEDULE) or book (SCHEDULE),
3 Reporters oust pest (‘reporters’ oust ‘pest’ = rorer = ERROR) by mistake (ERROR),
5 Sympathetic (WELL-DISPOSED) to Spring (spring = WELL-) cast out (-DISPOSE-) by deputy leader (‘Deputy’ leader = -D) (WELL-DISPOSED),
6 Latest (NEW-) on 100 metres dash (-SPRINT) (NEWSPRINT) all over The Paper (NEWSPRINT),
7 Introduction (LEAD-IN) to Heavy Metal (heavy metal = LEAD-) that’s fashionable (-IN) (LEAD-IN),
8 Disreputable debonair (RAKISH) artist (RA-) at The Lighthouse, Dublin (-KISH lighthouse, Dublin) (RAKISH),
11 Take five (take five = BREAK-) observing Ramadan (-FASTING) (BREAKFASTING) partaking of the first meal of the day (BREAKFASTING),
15 Gives up office (STEPS DOWN) for cats and dogs (pets) raised (= reverse indicator) (pets = STEP-) on top of Sperrins (top of ‘Sperrins’ = -S) in Northern Ireland (DOWN) (STEPS DOWN),
16 Public house (BAR-) gets it (-IT-) from one (-ONE) (BARITONE) type who’s good with numbers in a vocal way (BARITONE voice),
17 Female nags mate (female nag’s mate/mare’s mate = STUD- horse) sent (sent) off (= anagram indicator) (sent = -ENTS) (STUDENTS) with those who are still learning (STUDENTS),
19 Charged (DASHED) with this stroke – (this stroke “–” is a DASH-) alongside one of the journalists (editor = -ED) (DASHED),
20 It’s part of the plot (CASSIA tree/shrub) in Isaac’s (Isaacs) novel (= anagram indicator) (Isaacs = CASSIA),
23 Spar is out of pilchards (‘spar’ is out of ‘pilchards’ = ilchd = CHILD) – and that’s an issue! (CHILD).