Across:
1 Request (APPEAL) remuneration leaving European Parliament (“remuneration” leaving “European Parliament” = ppalae = APPEAL),
4 Most of the (n) grass (“lawn” without ‘n” = LAW) for playing tennis (COURT) (LAW COURT) is for The Suits (legal suits/cases for the LAW COURT),
9 Puts away (DRINKS) criminal (= anagram indicator) kinds (kinds = D-INKS) around ringleader? (“ring” leader = -R-) (DRINKS),
10 Pretend to be a player in drama (ACT A PART) for law (ACT) to be removed (apart = A PART) (ACT A PART),
12 Poor (= anagram indicator) Latin king (Rex = EX-R) welcomes Czech (“Czech” = “cheque” = -CHEQUE-) reports (= homophone indicator) (EXCHEQUER) produced by the Treasury (EXCHEQUER),
13 Protection (HEDGE) for characters in impoverished geopolitics (HEDGE characters/letters hidden in “impoverished geopolitics”),
14 Has a quick look at (CASTS A GLANCE) those in 23 down (“casts” = CASTS) getting head barman (attorney general = AG = A G-) to clean (clean = -LANCE) building (= anagram indicator) (CASTS A GLANCE),
18 Choosing your favourite singer, for instance (CASTING A VOTE), using Rod’s (using rods / fishing rods = CASTING) opening arrangement (opening “arrangement” = A) for ballad (“ballad” = “ballot” = VOTE) on the radio (= homophone indicator) (CASTING A VOTE),
21 Cultivated type (WHEAT) of women (W-) from The Sun (-HEAT from the sun) (WHEAT),
22 Manages (RUN S-) to show concern (-CARE-) for 500 (-D) (RUN SCARED) in panic (RUN SCARED),
24 Upsets (= reversal indicator) Pat (pat = TAP), Daniel (DAN-) and Clare (-CE) (TAP DANCE) in movement where one is bound to get loads of clicks (TAP DANCE),
25 Have ambitions (ASPIRE) for one of them in O’Connell Street (A SPIRE),
26 Tough (HARD) detective (DI-) from Saskatchewan (-SK) (HARD DISK) to drive with all the important information (HARD DISK drive),
27 A person of interest to those looking for criminals (extortionate moneylender = USURER) is confident (-SURE-) in old city (U-R) (USURER).
Down:
1 The House (AUDIENCE) could be watching 23 down (AUDIENCE could be watching “casts’” in plays),
2 Criminal (= anagram indicator) snipers (snipers = PRIN-ESS) caught (-C-) inside (PRINCESS) might still have a shot at the monarchy perhaps? (PRINCESS),
3 Trios getting out of oil tankers (“trios” getting out of “oil tankers” = lanke = ANKLE) for joint (ANKLE),
5 A (A-) carol (-S-ING) about tried and tested type (-CERTAIN-) (ASCERTAINING) of working out, for sure (ASCERTAINING)
6 Clips (clips/cuts “t”) of three conversations (chat x 3) (“chat + chat + chat” without “t” = CHA-CHA-CHA) in the dance hall (CHA-CHA-CHA),
7 Salinger leaves Guardian, as Glen (“Salinger” leaves “Guardian as Glen” = uadagn = UGANDA) is in Africa (UGANDA),
8 Nothing rare in air letters (nothing “rare” in “air letters” = iletts = TITLES) from a number of different addresses (TITLES),
11 The work of the Minister for Finance (BUDGET) is putting pressure (P-) on what Paddy produces (paddy field produces -RICES) (BUDGET PRICES) in the bargain basement (BUDGET PRICES),
15 Get this on your phone for your birthday (SMART CARD) for doing business without making contact perhaps (SMART CARD),
16 Representative (tour guide/courier = COUR-IER) swallows last pint (last “pint” = -T-) (COURTIER) nursing 2 down perhaps (COURTIER looks after “princess” perhaps),
17 Teacher (HEAD-) with a number of gowns perhaps (-GEAR) (HEADGEAR) and mortarboards (HEADGEAR),
19 Jerk (TWITCH) starting trouble (starting “trouble” = T-) is capable of casting a spell over someone (-WITCH) (TWITCH),
20 Assistance sought (HELP-) in hospital (-ER) (HELPER) for right-hand man (HELPER),
23 Goes fishing (CASTS) for more than one set of players (CASTS).