Across:
1 Beastly types (HIPPOS) from trendy (HIP-) post offices (POs = -POS) (HIPPOS),
4 Precious type (ADORABLE) of hammer (= anagram indicator) or a blade (or a blade = ADORABLE),
9 University worker (READER) familiar with Dubliners, for example (familiar with Joyce’s Dubliners, for example/the book = READER),
10 Fashionable (IN-) mobile (-ACTIVE) (INACTIVE) is not in service (INACTIVE),
12 Took care of business (-RAN-) in latest (latest) mess? (= anagram indicator) (latest = T-SLATE) (TRANSLATE) Give me that in plain English! (TRANSLATE),
13 As the labourers see it, excellent (PLUM- job) head on pint (head on ‘Pint’ = -P) (PLUMP) of stout (PLUMP),
14 Leave Kilmainham (GET OUT OF JAIL) with Oriental (East = -E-) illegal ticket seller (tout = -T OUT) in thick mist (fog) going back (= reverse indicator) (fog = G- OF) to Mountjoy (JAIL) (GET OUT OF JAIL),
18 Old glory (AMERICAN FLAG) for The New Yorker (AMERICAN) to point out (to FLAG) (AMERICAN FLAG),
21 Reference book (ATLAS) about time (at last) isn’t finished (t) (‘at last’ without ‘t’ = ATLAS),
22 Train (= anagram indicator) – leave on it (leave on it = ELEVATION) for one of The Heights (ELEVATION),
24 Cancels (RESCINDS) short (t) break (‘rest’ without ‘t’ = RES-) from college (-C-) with popular (-IN-) policeman (-DS) (RESCINDS),
25 Lancastrian misses train (‘Lancastrian’ misses ‘train’ = lancas = CANALS) going around Rialto (CANALS in Rialto, Venice),
26 Type (CATEGORY) of accountant (CA-), for example (e.g. = -EG-), invested in island (Tory island = -T-ORY) (CATEGORY),
27 Shows contempt (SNEERS) for salesperson dismissing opals (‘salesperson’ dismissing ‘opals’ = esersn = SNEERS).
Down:
1 The roots (HERITAGE) of one (-I-) child’s game (-TAG-) wrapped up in the present (HER-E) (HERITAGE),
2 Those in The Pod (PEAS-) lose the head (r) with angry outbursts (‘rants’ without ‘r’ = -ANTS) (PEASANTS) from old workers (PEASANTS),
3 Starts (OPENS) for Riga from Singapore (‘Riga from ‘Singapore’ = snpoe = OPENS),
5 DJ (DINNER JACKET) from hostelry (-INN-) in red (red) upset (= reverse indicator) (red = D-ER) by part of the suit (JACKET) (DINNER JACKET),
6 Party (RECEPTION) is on the way into Office (RECEPTION),
7 Take oils out of boiler suit (take ‘oils’ out of ‘boiler suit’ = beruit = BEIRUT) from the Mediterranean port (BEIRUT),
8 Let off the hook (EXEMPT) by former partner (EX-) and is mostly (y) unoccupied (‘empty’ without ‘y’ = -EMPT) (EXEMPT),
11 Unskilled worker (labourer = LABOUR -ER) getting to grips with Heavy Metal (LEAD-) (LABOUR LEADER) is in charge of the party (LABOUR LEADER),
15 A foreign (a = UN-) maiden (-M-) making inquiries (-ASKING) (UNMASKING) is getting exposure (UNMASKING),
16 Fundamental (ULTIMATE) sect (cult) loses leader (c) (‘cult’ without ‘c’ = ULT-) and one (-I-) confidante (-MATE) (ULTIMATE),
17 Feels uneasy (AGONISES) as adaptation (= anagram indicator) is on ages (is on ages = AGONISES),
19 Financial authority opens (‘Financial Authority’ opens = FA-) unfinished (k) building unit (‘brick’ without ‘k’ = -BRIC) (FABRIC) previously sold by the yard (FABRIC sold by the yard/meter),
20 Keeps The Suits in check (CLOSET) within earshot of (CLOSE-) the leadership (‘The’ leadership = -T) (CLOSET),
23 Part of Malaga invokes (part of ‘MalAGA INvokes’ = AGAIN) another time (AGAIN).