Across:
1 State (= homophone indicator) campaign ('canvass' = 'CANVAS') – what's intent? ("what's intent" = "what's in tent" = CANVAS),
4 Take drugs (SMOKE POT) to cure (SMOKE) head (top) in a roundabout way (= reverse indicator) (top = POT) (SMOKE POT),
9 Fool (NITWIT) of identical twin dismisses nice lad (‘identical twin’ dismisses ‘nice lad’ = intitw = NITWIT),
10 A Ted – teen (a ted teen) rebel (= anagram indicator) (a ted teen = ATTENDEE) and the one at the event (ATTENDEE),
12 Corgi seen (corgi seen) out (= anagram indicator) (corgi seen = RECOGNISE) of place (RECOGNISE),
13 First cousin dismisses crisis (‘first cousin’ dismisses ‘crisis’ = ftoun = FOUNT) in spring (FOUNT),
14 Didn’t overlook anything (CONCENTRATED), as to not lose Focus (to CONCENTRATE-) on back road (back ‘roaD’ = -D) (CONCENTRATED),
18 Amazement (ASTONISHMENT) in a (A-) street (-S-T) over Shinto (Shinto) movement (= anagram indicator) (Shinto = -TONISH-) with people (-MEN-) (ASTONISHMENT)
21 Pointer (ARROW) to a (A-) royal (-R-) line (-ROW) (ARROW),
22 Forsaken (ABANDONED) by Russell (A-E-) around place in Cork (-BANDON) close to Castletownsend (close to/last letter of ‘castletownsenD’ = -D) (ABANDONED),
24 Attractive (MAGNETIC) periodical (MAG-) on the web (-NET-) for single (-I-) clubs (-C) (MAGNETIC),
25 Opine (opine) wildly (= anagram indicator) (opine = PI-EON) about golf (-G-) (PIGEON) in The Messenger (PIGEON),
26 Drop (DECREASE) Declan (DEC-) Rice, initially (‘Rice’ initially = -R-) with no difficulty (with -EASE) (DECREASE),
27 Sailor (-TAR-) has time (-T-) in boat (S-S) (STARTS) for the new jobs (STARTS).
Down:
1 Enter into an arrangement (CONTRACT) with shrink (shrink/get smaller = CONTRACT),
2 Becoming aware (NOTICING) Dan is out of gin and tonic (‘Dan’ is out of ‘gin and tonic’ = gintonic = NOTICING),
3 Getting on (AGING) with top lawyer (Attorney General = AG-) in (-IN-) Government (-G) (AGING),
5 Type of round figures (MATHEMATICAL) describing those in the Book of Numbers (MATHEMATICAL book of numbers),
6 Chill (KEEP FRESH) in castle (KEEP) with novel (novel = FRESH) (KEEP FRESH),
7 Holding the top three places (for winners = PODIUM) for opium (opium) production (= anagram indicator) (opium = PO-IUM) around delta (-D-) (PODIUM),
8 Attorney is not getting on (‘attorney’ is not getting/ without ‘on’ = attrey = TREATY) – it follows a major conflict (TREATY),
11 In a manner of speaking (DICTION-), raise (raise) doubts (= anagram indicator) (raise = -ARIES) (DICTIONARIES) these are wordy reference books (DICTIONARIES),
15 The foreign (‘the’ foreigh = EL-) society (-S-) with English (-E-) women (-W-) present (-HERE) (ELSEWHERE) in a different place (ELSEWHERE),
16 Dancer’s partner (Dancer = REINDEER) is a present-day worker? (‘present day’ = Christmas day worker = REINDEER),
17 Female nags mate (female nag’s mate/mare’s mate = STUD- horse) sent (sent) off (= anagram indicator) (sent = -ENTS) (STUDENTS) with those classy types (STUDENTS),
19 Cultivated grapes, for instance (FARMED), in solid frame without soil? (‘solid frame’ without ‘soil’ = dframe = FARMED),
20 Temperature (T-) reflects (= reversal indicator) most of (y) Gary (‘GARy’ without ‘y’ = gar = -RAG-), Indiana – to begin with (‘Indiana’ to begin with = -I-), it’s cold (-C) (TRAGIC) and dreadful (TRAGIC),
23 Wander (DRIFT) from Dublin (D-) to Split (split = -RIFT) (DRIFT).