Across:
1 Responsible (LIABLE) for a libel (a libel) action (= anagram indicator) (a libel = LIABLE),
4 Heads to Catania, Rimini, Imola (heads to ‘Catania Rimini Imola’ = CRI-) and Milan (Milan) working (= anagram indicator) (Milan = -MINAL) (CRIMINAL) for The Don (CRIMINAL),
9 Made a home (NESTED) out of necessity (NE-ED) across the street (-ST-) (NESTED),
10 CID react (CID react) badly (= anagram indicator) (CID react = ACCREDIT) to a scribe? (‘a scribe’ = ‘ascribe’ = ACCREDIT),
12 With all the seats taken in The Dáil (FULL HOUSE), it gives one the upper hand perhaps (FULL HOUSE in poker),
13 Promise a selection in part (‘promisE A SELection’ in part = EASEL) to artist’s supporter (EASEL),
14 A job for a snoop (LETTER OPENER) in 27 across (‘letter’ = LETTER) with Frank (OPEN-) Ward (-ER) (LETTER OPENER),
18 Correspondent (LETTER WRITER) opens 14 across (‘letter opener’ = LETTER) with bookmaker? (‘book maker’ = WRITER) (LETTER WRITER),
21 Ability to act (POWER), step forward, releasing drafts (‘step forward’ releasing ‘drafts’ = eporw = POWER),
22 Honouring (ENNOBLING) old French maid (bonne) serving up (= reverse indicator) (bonne = ENNOB-) fish (-LING) (ENNOBLING),
24 The bare bones (NO-FRILLS) of dressmaker’s policy that takes the edge off (NO-FRILLS),
25 Adore (adore) novel (= anagram indicator) (adore = ORDEA-) following K (-L is following ‘k’) (ORDEAL) in The Trial (ORDEAL),
26 Gave up on (RESIGNED) dress (= anagram indicator) designer (designer = RESIGNED),
27 For example, a (A = LETTER) fragment of secret telephone turns-up (= reverse indicator) (fragment of ‘secRET TELephone’ = retter = LETTER).
Down:
1 Left (L-) with revolting (= reverse indicator) genetic stuff (DNA = -AND-) to seal (-FILL) (LANDFILL) waste material in the ground (LANDFILL),
2 Beau lost (beau lost) out (= anagram indicator) (beau lost = ABSOLUTE), as the ruler had this type of power (ABSOLUTE power),
3 Scrounger (LEECH), on reflection (= reversal indicator), on the back foot (heel = LEE-H) getting to grips with (= reversal indicator) cold (-C-) (LEECH),
5 Loud music (RACKET-) from Spain (-E-) by top-end (top ‘End’ = -E-) wedding band (-RING) (RACKETEERING) working with 4 across, for instance (working with ‘criminal’ RACKETEERING),
6 Pusher (MARKETEER) in commercial area (MARKET-) taking drugs (E+E = -EE-) to get head right (head ‘Right’ = -R) (MARKETEER),
7 Has a reputation for exposing (NUDISM) type of philosophy that’s always revealing (NUDISM),
8 Accommodation (let = -TEL-) going up (= reverse indicator) in place (lay = LA-Y) (LATELY) in recent times (LATELY),
11 Without warning (OUT OF THE BLUE), no longer playing for The Dubs perhaps (OUT OF THE BLUE),
15 Distance education through Zoom (E-LEARNING) mismanaged (= anagram indicator), in general (in general = E-LEARNING),
16 Emailed (S-ENT) over tax (DIRT tax) return = (reverse indicator) (DIRT = -TRID-) (STRIDENT) – it sounds really harsh! (STRIDENT),
17 One can’t stay still (WRIGGLER) in river (-R) behind (= position indicator) snake (WRIGGLE-) (WRIGGLER),
19 Old-age pensioner fails to get alongside (‘old-age pensioner’ fails to get ‘alongside’ = peoner = OPENER) for first game (OPENER),
20 Even Twain (even letters of ‘tWaIn’ = -WI-) has the odd fit (odd letters in ‘FiT’ = -FT-) in ship (SS = S-S) (SWIFTS) with flighty types (SWIFTS),
23 By and large Dylan is missing (‘by and large’ ‘Dylan’ is missing/without ‘Dylan’ = barge = BARGE) lighter? (flat-bottomed BARGE).