Across
1 Reportedly pared (homophone of ‘pared’ = ‘paired’ = BINARY) nib back (= BIN) within a year (includes ‘A YR’).
4 Gets level (= FLAT LINE) from studio (= FLAT) cue, by the sound of it (i.e. ‘queue’ = LINE).
9 Shrewd (= ASTUTE) to use last substitute (‘last substitute’ = TUTE) as (= AS) player (indicates anagram).
10 Direct one (= STRAIGHT) to channel, orally (homophone for ‘strait’.
12 Idle tuner (= IDLE TUNER) goes off (indicates anagram) briefly, during performance (= INTERLUDE).
13 Shocking (= TASER) and revealing (indicates hidden word) Buena Vista series (buena visTA SERies).
14 Drunken, draining boor (= anagram of DRAINING BOOR) is oppressing one by the sound of it (i.e. sounds like ‘pressing one’ = IRONING BOARD).
18 It’s hard to play guitar this way (i.e. ‘single-handed’) without assistance (= SINGLE-HANDED).
21 Awestruck (= AGAPE), head academic (= A) turned (indicates anagram) page (= PAGE).
22 Review (= RE-EXAMINE) about (= RE) former (= EX) Austrian leader (= A) belongs to me (= MINE).
24 Such counselling (= GUIDANCE) might uncage id by mistake (anagram of ‘uncage id’ = GUIDANCE).
25 Cut (= DIVIDE) the end off the film (i.e. ‘video’ without ‘o’ = VIDE) I’d returned (= DI) to make (indicates anagram).
26 Turns out (indicates anagram) the little sister (= SIS) of the poet and painter here (= YEATS) wrote many academic pieces. (= ESSAYIST)
27 It’s usual to wear white for this (= TENNIS) Argentinian dance (i.e. ‘tango’ = T) in Clare (= ENNIS).
Down
1 I hear Angelica (homophone of ‘Angelica’ i.e. ‘angelic’ = BEATIFIC) bit (= BIT) into one (= I) in café (= CAFE).
2 Composer works (= NOTATION) at it (= AT IT) around (indicates anagram) midday (= NOON).
3 Goes round and round (= ROTOR) or back and forth (i.e. contains ‘or’ and ‘ro’ and is a palindrome).
5 Initially (i.e. ‘initial’ = ‘letter opener’) sharp (i.e. implement to open post), perhaps? (= LETTER OPENER)
6 Cavort with (indicates anagram) traitor at (= TRAITOR AT) restaurant (= TRATTORIA).
7 Swallow (= INGEST) might sing (SING) with swift, finally (= T), at the end of June (=E).
8 Will find food here (= EATERY) but might take outside (‘take outside’ = TE) of a year (= YEAR), roughly (indicates anagram).
11 Clark (CLARK) gets eggs (EGGS) in August (AUG) and carelessly (indicates anagram) stows them here (= LUGGAGE RACKS).
15 Plans to travel (= ITINERARY) about (= RE) from top to bottom of Italy (= I-Y) by train (= TRAIN), capriciously (indicates anagram).
16 Snake starts (i.e. start of ‘adders’ = ADD) getting into (= INTO) one (= I) and increases in quantity (= ADDITION).
17 Crazy (indicates anagram) geese (= GEESE) on LSD (= LSD) have no boundaries (= EDGELESS).
19 This might destroy (i.e. MANGLE) outfit - use14 across instead (ref. ‘ironing board’ used now instead of mangle).
20 It’s said (indicates homophone) these are wrongs committed in sea inlets (i.e. homphone for ‘bay sins’) or areas drained by rivers (= BASINS).
23 Strong wind (= GALE) in Irish capital (= I) moves quickly (= AGILE).