Across:
1 Bug (CICADA) in police department (CID = CI-D) captures assistant commissioner (assistant commissioner = AC) backtracking (= reversal indicator) (AC = -CA-) on answer (-A) (CICADA),
4 In my opinion (AS I SEE IT), most of the continent (most of ‘Asia’ = AS I) get the picture (SEE IT) (AS I SEE IT),
9 Landlord (SQUIRE) of mates leaving Times Square (‘mates’ leaving ‘Times Square’ = isqure = SQUIRE),
10 Smashing time (BREAKAGE) presumably, that’s out of most people’s hands (BREAKAGE),
12 Up on Maine (up on Maine = PNEUMONIA) compound (= anagram indicator) – it’s infectious and could go viral (PNEUMONIA),
13 Lubricated (OILED) agent is not part of delegation (‘agent’ is not part of ‘delegation’ = delio = OILED),
14 Insensitive (THICK-SKINNED) to local fools (THICK-S-) from family (-KIN-) getting to study (den) review (= reversal indicator) (den = -NED) (THICK-SKINNED),
18 Search (-COMB-) in the near future (anon) coming back (= reversal indicator) (anon = NON-A-) to taunt (taunt) heartless (u) (‘taunt’ without ‘u’ = TANT) (NON-COMBATANT) person not part of campaign (NON-COMBATANT),
21 Vacancy (BLANK) in financial foundation (‘financial’ foundation = -L-) welcomed by lender (B-ANK) (BLANK),
22 Shot (= anagram indicator) in a camera (in a camera = AMERICANA) by Hollywood and Disney, for instance (AMERICANA),
24 Paper (SUN- newspaper) boudoirs, kitchens, parlours (-ROOMS) (SUNROOMS) and the warmest spaces in the house (SUNROOMS),
25 Polish off (FINISH) one of those produced in Europe (‘Finnish’ = ‘FINISH’), by the sound of it (= homophone indicator),
26 Looks after expectant fathers (SEMINARY) meeting (SEMINAR-) on the Fourth of July (fourth of ‘July’ = -Y) (SEMINARY),
27 Doesn’t (doesn’t = STONED) disturb (= anagram indicator) those on drugs (STONED).
Down:
1 They store the leftovers (CESSPITS) in ridiculous (= anagram indicator) steps (sic) (steps sic = CESSPITS),
2 Helix (coil = C- OIL) welcomes risqué (-RUDE) (CRUDE OIL) alternative to Grease? (CRUDE OIL),
3 Digs up riches under macaroni heads (‘digs up riches under macaroni’ heads = DURUM) of wheat (DURUM wheat),
5 Sounds like (= homophone indicator) something from Breakfast (‘cereal’ = ‘SERIAL) Menu (menu = NUM-E-) designed (= anagram indicator) around top bread (top ‘bread’ = -B-) and butter ultimately? (‘butter’ ultimately = -R) (SERIAL NUMBER) On Your Bike! (SERIAL NUMBER),
6 Sound of Antrim tops (‘sound of Antrim’ tops = SOA-) sound of Cork (P OP- = sound of cork) – and, for a generation (-ERA) (SOAP OPERA), it’s a never-ending story (SOAP OPERA),
7 Authorise (ENABLE) to remove knits from linen basket (remove ‘knits’ from ‘linen basket’ = lnegae = ENABLE),
8 Up-to-date (TRENDY) checkout (check out = TR-Y) incorporating limitless (d) cash advance (‘lend’ without ‘l’ = -END-) (TRENDY),
11 Incites legless types to move to music (SNAKE CHARMER) and do the twist (SNAKE) with ladies’ man (CHARMER) (SNAKE CHARMER),
15 You can see this in Ring at times (KNOCK DOWN) and two other places in Ireland (Knock + Down = KNOCK DOWN),
16 Vain Arab (vain Arab = BAVARIAN) showing off (= anagram indicator) at home in Munich (BAVARIAN),
17 Stick to (ATTACH-) key (music key -E-) forward on the wing (‘forward’ on the wing = -D) (ATTACHED) for United (united = ATTACHED),
19 Persecutes (ABUSES) sailor (able-bodied seaman = AB-) who takes drugs (-USES) (ABUSES),
20 Relative (M-UM) embraces head barman (Attorney General = -AG-) opening new (opening ‘new’ = -N-) (MAGNUM) large bottle of wine (MAGNUM),
23 Foolish type (IDIOT) of name comes out of mediation (‘name’ comes out of ‘mediation’ = ditio = IDIOT).