Across:
1 Poses (sits = -STIS) for agency (Associated Press = AP) raising (= reversal indicator) (AP = PA-) (PASTIS) a drink (PASTIS),
4 Various types (ASSORTED) initially at (initially ‘At’ = A-) the heart of (s) Essex (the heart of ‘esSex’ = -S-) and rocky (= anagram indicator) Dorset (Dorset = -SORTED) (ASSORTED),
9 Job for a policeman (BEAT) involved in Pulse? (Information Technology/IT is involved in the Pulse Garda computer system = IT) (BEAT IT) Get out of here! (BEAT IT),
10 Rome reps (Rome reps) working (= anagram indicator) (Rome reps = EMPERORS) for those expanding into other countries (EMPERORS),
12 Trim (p) agent (‘rep’ without ‘p’ = RE-) and Bond (-COMBINE) (RECOMBINE) to marry again (RECOMBINE),
13 It is not found in Tel Aviv (‘it’ is not found in ‘Tel Aviv’ = elavv = VALVE) and not having it, you’ve no control on the pressure (VALVE),
14 Bar (WATERING HOLE) the feeding of plants (WATERING) with 21 across (holes) briefly (s) (‘holes’ without ‘s’ = HOLE) (WATERING HOLE),
18 What you might have to do looking for love, perhaps? (TREASURE HUNT) Chase (HUNT) darling (TREASURE) from the start! (= position indicator) (TREASURE HUNT),
21 Openings (HOLES) for short breaks (short holidays = hols = HOL-S) around Spain (-E-) (HOLES),
22 Goes to the dogs (GREYHOUND racing) with American coach (GREYHOUND bus/coach),
24 Piece (AR-M-) covers article (-A-) by Russell (-AE- Russell) – an (-AN) (ARAMAEAN) old person from Syria (ARAMAEAN),
25 Capital of Aruba (capital/money of Aruba = FLORIN) – I wouldn’t give you two shillings for it, but everyone else would? (two shillings was the value of a FLORIN),
26 Costly (STEEP-) for the French (the = -LES) (STEEPLES) types over places of worship (STEEPLES),
27 Finishes with 5 down (finishes ‘summer houses’ = HOUSES) in The Dáil and The Seanad (HOUSES).
Down:
1 Creep (CRAWL) follows (= position indicator) a stout dealer (PUB) (PUB CRAWL) on local tour (PUB CRAWL),
2 Small (S-) vehicle (-CAR-) from Detroit, for example (-CITY) (SCARCITY), in short supply (SCARCITY),
3 Type of bone gynaecologist might recognise (part of the pelvis = ILIUM bone) in Helen’s city? (ILIUM = another name for Troy / Helen of Troy),
5 Belvedere’s (Belvederes = SUMMER HOUSES) type of school (SUMMER school) diets (diets/parliaments = HOUSES) (SUMMER HOUSES),
6 Exaggerate the importance of (OVERVALUE) veteran (vet) endlessly (‘vet’ without ‘t’ = -VE-) in a Louvre (a Louvre = O-RVALUE) building (= anagram indicator) (OVERVALUE),
7 Ford (Model T-) and Royce’s partner (-ROLLS Royce) (TROLLS) causing trouble on site (TROLLS),
8 Charged (DASHED) with this stroke – (this stroke “–” is a DASH-) alongside one of the journalists (one of the journalists = editor = -ED) (DASHED),
11 Handy way of replying (SIGN LANGUAGE) that allows some people to be heard? (SIGN LANGUAGE),
15 Might have been licked in the past but won’t be licked again (RARE STAMP) – presumably you got that from an old man of letters? (RARE STAMP),
16 Check out local (‘local’ suss = SUS-S) taking in old city (-UR-) going to Russia (-RU-) (SUSURRUS) for the rustling, in the literary sense (SUSURRUS),
17 They’re bound to learn lessons (STUDENTS) as head of services (head of ‘Services’ = S-) expresses disapproval (tuts = -TU-TS) over library (-DEN-) (STUDENTS),
19 Leading cyclist (leading ‘Cyclist’ = C-) warms up (-HEATS) (CHEATS) with those taking drugs in race, for instance (CHEATS),
20 Make someone feel good (PLEASE) in suit? (suit/flatter = PLEASE),
23 Often the first thing out of characters’ mouths (HELLO) in The Inferno (HELL-) is to do with love (-O) (HELLO).