Across:
1 Judge (R-ATE) puts away engineering (-E-) bachelor (-B-) (REBATE) offering a reduction on the tariff (REBATE),
4 Cordial (AMICABLE) produced by nice friend (Nice/French ‘friend’ = AMI-) – a guy from The Telegraph perhaps (-CABLE) (AMICABLE),
9 Heal or (heal or = LAHORE) cure (= anagram indicator) in Asian city (LAHORE),
10 Fences off (ISOLATES) aisles to (aisles to = ISOLATES) building (= anagram indicator),
12 Pheasant (GAME-) from small (-S) kitchen (ROOM) (GAMES ROOM) is a favourite with the players (GAMES ROOM),
13 Give out (ALLOT) to OAP from Palo Alto (‘OAP’ from ‘Palo Alto’ = lalto = ALLOT),
14 It’s a big relief (THANK HEAVENS) reservoir (T-ANK) around hotel (-H-) is open when it rains heavily (when the HEAVENS open) (THANK HEAVENS),
18 At the start of 12 across (start of ‘games room’ = GAMES-), staff (-MAN-) on despatch (-SHIP) (GAMESMANSHIP) involved in psychological tricks (GAMESMANSHIP),
21 Play (= anagram indicator) a disc (a disc = ACIDS) produced by The Chemical Brothers presumably (ACIDS),
22 Giving someone entitlement (ENNOBLING) to excite (= anagram indicator) Nigel (Nigel = E-LING) welcoming Bonn (Bonn = -NNOB-) back (= reverse indicator) (ENNOBLING),
24 Card (card = -RD CA-) forger (= anagram indicator) consumed by drugs (hash = HA- -SH) (HARD CASH) and ready money (HARD CASH),
25 Locked up in Ankara, Biarritz (Locked up in ‘Ankara, Biarritz’ = ARABIA) and in several Asian countries (ARABIA),
26 Shady types (PARASOLS) from MIT not into pastoralism (‘MIT’ not into/out of ‘pastoralism’= pasorals = PARASOLS),
27 Ship (S-S) goes around a (-A-) port (Tyre) endlessly (e) (‘Tyre’ without ‘e’ = -TYR-) (SATYRS) with mythical revellers with a reputation for being drunk (SATYRS).
Down:
1 Put it down (RELEGATE) to writing (from 3Rs = R-) to English (-E-) emissary (-LEGATE) (RELEGATE),
2 Unconventional (BOHEMIAN) bar (ban = B-AN) takes in home (home = -OHEM-) cooking (= anagram indicator) on island (-I-) (BOHEMIAN),
3 Turns up (= reversal indicator) group (set = TE-S) holds onto address (Mr = -RM-) (TERMS) – it comes with conditions (TERMS and conditions),
5 Type of production (MASS production) from the symphony (MOVEMENT) (MASS MOVEMENT) in March (march = MASS MOVEMENT),
6 One of those from Irish kitchen (COLCANNON) in the army (colonel = COL-) is likely to be fired (-CANNON) (COLCANNON),
7 Characters in Roosevelt tableau vivant (characters in ‘Roosevelt tableau vivant’ = elttab) reflecting (= reversal indicator) (elttab = BATTLE) major conflict (major/army conflict BATTLE),
8 Not genuine (ERSATZ) rates (rates = ERSAT-) laid out (= anagram indicator) for the last of the fizz (last of the “fizz” = -Z) (ERSATZ),
11 For character in Trading Places (ROLE REVERSAL), it’s a case of poacher turned gamekeeper (ROLE REVERSAL),
15 On the weekend (on the ‘week’ end = K-) drop off (-NAP-) with bags (-SACKS) (KNAPSACKS) of back numbers for The Ramblers (KNAPSACKS),
16 Singer (CHOIRBOY) in Switzerland (CH-) and in Brazil (Rio = -OIR-) set up (= reversal indicator) by young male (-BOY) (CHOIRBOY),
17 Sally’s (sallies = EPIGRAMS) Oriental (east = E-) farm animals (pig + rams = -PIGRAMS) (EPIGRAMS),
19 Walk on summit (‘walk’ on summit = W-) and in the forest (-ASH) with small dog (pup) heading off (p) (‘pup’ without ‘p’ = UP) (WASH UP) to drift onto the beach (WASH UP),
20 Copy (MIRROR) of the paper? (MIRROR),
23 Some of those in Birmingham rubbished (some of those in ‘Birmingham rubbished’ = amrub) cover-up (= reversal indicator) (amrub = BURMA) in the old country (BURMA).