Across:
1 In my book (LEAVES), the forecasters will read something into these (the forecasters/fortune-tellers will read something into these = tea LEAVES),
4 A (A) bad (bad = DAB) review (= reversal indicator) by leading horticulturist (leading ‘horticulturist’ = H-) and (-AND) (A DAB HAND) an expert in a particular field (A DAB HAND),
9 Hostility (ENMITY) to engineering (E-) college overseas (Massachusetts Institute of Technology = -MIT-) in US city (-N-Y) (ENMITY),
10 Took off (PARODIED) from Knock (knock/rap = PAR-) going back (= reversal indicator) to Oxford (-O-) and stopped working (-DIED) (PARODIED),
12 Horseplay perhaps (POLO) after (= positional indicator) drink (WATER) (WATER POLO) leads to game of pool? (WATER POLO),
13 Drop (DRAPE) of DNA taken from red panda (‘DNA’ taken from ‘red panda’ = repad = DRAPE),
14 What loyalist said he’d do (KEEP ONE’S WORD) in The Castle (KEEP) for individuals (ONE’S) for part of the sentence (WORD) (KEEP ONE’S WORD),
18 Only the man upstairs was there for premiere (OPENING NIGHT) of The Big Bang perhaps (OPENING NIGHT),
21 Rig comes off ring road (‘rig’ comes off ‘ring road’ = nroad = ADORN) in Trim (ADORN),
22 Lament (SHED A TEAR) for potential partner (date = -D A TE-) in clip (shear = SHE- -AR) (SHED A TEAR),
24 Alumni (Alumni = LUMINA-) made up (= anagram indicator) a fair amount of (half of) jury (half of ‘jury’ = -RY) (LUMINARY) with inspirational leader (LUMINARY),
25 Bring up (-RAISE) after (= position indicator) Power (P-) (PRAISE) offers commendation (PRAISE),
26 Exercises (PRESS-UPS) little dogs (P-UPS) burying most of (c) the salad stuff! (‘cress‘ without ‘c’ = -RESS) (PRESS-UPS),
27 Furlong (F-) got along (along = -LAGON) badly (= anagram indicator) (FLAGON) – is it the bottle? (FLAGON).
Down:
1 Piece of fiction (LIE) celebrating The Dead (a wake = AWAKE) (LIE AWAKE) – it’s something to experience if one is not out for the night (LIE AWAKE),
2 Conceded (ADMITTED) New (= anagram indicator) Media (Media = ADMI-E-) is about race (-TT- race) to deliver capital (‘deliver’ capital = -D) (ADMITTED),
3 Peter Pan releases app (‘Peter Pan’ releases ‘app’ = etern = ENTER) that’s key to computer (ENTER key),
5 Is not working (DEAD) with old (O-) lead in Fame (lead in ‘fame’ = -F) for the season (WINTER) (DEAD OF WINTER) when it’s coldest (DEAD OF WINTER),
6 Book (B-) on The Street (-ROAD) is hard work (grind) for the most part (d) (‘grind’ without ‘d’ = GRIN) (BROAD GRIN) or brings a smile to one’s face? (BROAD GRIN),
7 A Milan (A Milan = ANIMAL) butcher (= anagram indicator) provides food for the meat eaters (ANIMAL),
8 Tremble walking (DODDER) and running through Dublin (DODDER),
11 Freak out (LOSE ONE’S GRIP) with release (LOSE ONE’S GRIP),
15 Pop (pop = OPP-) out (= anagram indicator) with individual (-ONE-) workers (ants) losing the head (a) (‘ants’ without ‘a’ = -NTS) (OPPONENTS) with the critics (OPPONENTS),
16 Having the same opinion as (AGREEING) top lawyer (Attorney General = AG-) finding drugs (Es = -EE-) hidden by wedding band (R-ING) (AGREEING),
17 Endless (end ‘less’ = S-) time (-T-) to encourage (urge on = -URGEON) (STURGEON) one of those from school (STURGEON from school of fish),
19 Allow (allow = WALLO-) cook (= anagram indicator) to prepare starter (‘prepare’ starter = -P) (WALLOP) in batter (WALLOP),
20 Stylish (cool) short (l) (‘cool’ without ‘l’ = COO-) Frenchman (Monsieur = -M-) gets to ask for money (beg) briefly (b) (‘beg’ without ‘b’ = -BE) (COOMBE) for the hospital deliveries in Dublin (COOMBE),
23 Meant to get out of Parliament (“meant” to get out of “Parliament” = parli = APRIL) after march (after March is APRIL).