Across:
8 Upsets (= reversal indicator) everyone (all = -LLA-) in bar (rod = DO-R) (DOLLAR) in foreign capital (foreign capital/money = DOLLAR),
9 Mad plot (mad plot) organised (= anagram indicator) (mad plot = D-PLOMAT) around one (-I-) (DIPLOMAT) running a mission (DIPLOMAT),
10 Knocking back (= reverse indicator) vessels (vessels /pots = STOP) of Scotch? (scotch/put an end to = STOP),
11 Will need to be composed (SHEET MUSIC), as someone could be sleeping on this (SHEET) rock (rock MUSIC) (SHEET MUSIC),
12 All the voices together (UNISON) in unruly intro (‘Unruly’ intro = U-) to popular (in) uplifting (= reverse indicator) (in = -NI-) short (g) ballad (song) (‘song’ without ‘g’ = -SON) (UNISON),
14 Never eat (never eat) out (= anagram indicator) (never eat = VENERATE) of respect (VENERATE),
15 8 across (‘dollar’ = DOLLAR) and most of 9 across (most of ‘diplomat’ = DIPLOMA-) take creativity to the extremes (‘CreativitY’ to the extremes = -CY) (DOLLAR DIPLOMACY) with the use of financial power overseas from us? (use of financial power overseas from US/United States = DOLLAR DIPLOMACY),
18 Esther edges away (‘e’ + ‘r’) (‘EstheR’ without ‘er’ = -STHE-) after (= position indicator) Russell (AE- Russell) finds Lawrence (-TE Lawrence) (AESTHETE) is sensitive to arty types (AESTHETE)
20 Is about (RE-) to join Munster, for one (-SIDE) (RESIDE), and stay there (RESIDE),
22 Can’t get enough (INSATIABLE) of Aliens (Aliens) adaptation (= anagram indicator) (Aliens = INSA-LE) about revolting (= reverse indicator) worm (bait = -TIAB-)? (INSATIABLE),
24 Those at the end at 13 down for the most part (s) (at the end of ‘split hairs’ without ‘s’ = HAIR) will grow on you (HAIR),
25 Put the fear of God into (SCARE OFF) sweetheart (‘swEet’ heart = -E) with hole (-O-) in neck warmer (scarf = SCAR -FF) (SCARE OFF),
26 Tears (SPLITS) from those in 13 down starting (those in ‘split hairs’ starting = SPLIT-) school (-S) (SPLITS).
Down:
1 Perfectionists dismiss priciest ('perfectionists' dismiss 'priciest' = eftons = SOFTEN) cushion (SOFTEN),
2 Bring the house down (CLAP) for those characters tied up (= reverse indicator) in Oedipal complex (for those characters in ‘oediPAL Complex’ = palc = CLAP),
3 Ripens or (ripens or) develops (= anagram indicator) (ripens or = PRISONER) in the cell (PRISONER),
4 Those captured by David Lean (those captured by ‘davID LEan’ = IDLE) out of a job (IDLE),
5 Turned up (= reverse indicator) no (no = - ON) pieces of clothing (tops = SPOT) (SPOT ON) 100 per cent perfect (SPOT ON),
6 Fish (cod) served up (= reverse indicator) (cod = DOC-) with wee drink (-DRAM-) in America (US = -U-S) at an opening (‘An’ opening = -A-) (DOCUDRAMAS) for those playacting in the real sense (DOCUDRAMAS),
7 Playing (= anagram indicator) CD as it is (CD as it is = SADISTIC), is really mean (SADISTIC),
13 Small (S-) clip of (e) graceful type (‘lithe’ without ‘e’ = -LIT H-) in Paris (Paris) resolving (= anagram indicator) (Paris = -P -AIRS) (SPLIT HAIRS) to be pedantic (SPLIT HAIRS),
14 Order (-O-) in disgusting (vile = V-ILE) (VOILE) material one can see through (VOILE),
16 Presumably, the administrative department in Provence-Alpes-Côte d’Azur (in France, ‘over Nice’ = OVERNICE) is excessively fastidious (OVERNICE),
17 Big (LARGE-) ship (-SS-) linked to oriental (East = -E) (LARGESSE) charity (LARGESSE),
19 Runs daily (runs daily/newspaper = EDITOR) and rides out without us (‘rides out’ without ‘us’ = rideot = EDITOR).
21 Small, pretty (DAINTY) local dinky (local ‘dinky’ = DAINTY),
23 Polish (BUFF) buying up starters (‘Buying Up’ starters = BU-) for party (Fianna Fáil = -FF) (BUFF).
24 Some Manilla hemp turns up (= reverse indicator) (some ‘maniLLA Hemp = llah = HALL) on the campus for the students (HALL).