ACROSS
8 - Endure response to dyspepsia perhaps (7,8) - STOMACH REACTION {STOMACH} {REACTION}
10 - Pharmacy gives note in a box (7) - CHEMIST {CHE{MI}ST}
11 - Company man's silent about travel to and from work (7) - COMMUTE {C}{M}{MUTE}
12 - A small piece of land in the middle of a sea? Sounds like one in between a sea of people (4) - ISLE (~aisle)
13 - I include a detail about a Greek mathematician (9) - EUCLIDIAN*
15 - Unsullied hermit caught out, embraced second of Apsaras (7) - ASEPTIC {AS(-c)E(+p)PTIC}
17 - Overdose of direct messages for doctor is something unusual (7) - ODDMENT {OD}{DM}{ENT}
19 - A part of the meiosis process — name, explanation initially seen in degree (9) - DIPLONEMA {DIPLO{N}E}MA}
21 - Great boxer followed by one to the Hawaiian chief (3,1) - ALI'I {ALI}{I}
24 - Most of the time America's superior to a friendly nation (7) - USUALLY {US}{U}{ALLY}
25 - Point — right one taken lying down (7) - DORMANT {DO{R}{MAN}T}
26 - Hurriedly lift dried banana roti perhaps (6,4,5) - INDIAN FLAT BREAD*
DOWN
1 - Intimidate someone with readings of autopsy characteristics (5) - PSYCH [T]
2 - Memory devices given to son to grasp knowledge (6) - (Addendum - TOKENS - {TO}{KEN}{S} - Left out by mistake)
3 - Pole was cut by headless weapon says evidence (8) - MANIFEST {MA{kNIFE}ST}
4,22 - O right, frames cheat eye unfairly in a painting (3,9,2,6) - THE TREACHERY OF IMAGES*
5 - Small group has one prawn dish (6) - SCAMPI {S}{CAMP}{I}
6 - Carving from tree on old city in the east (8) - FIGURINE {FIG}{UR}{IN}{E}
7 - In merchant navy without God's protection (9) - INDEMNITY {IN}DEMNITY Anno pending (Addendum - {IN}{DE{MN}ITY} - See comments}
9 - Different type of pay-load science reference books (14) - ENCYCLOPAEDIAS*
14 - Gave money to European Union to fit educational method (9) - PAIDEUTIC {PAID}{EU}{TIC} Couldn't connect 'TIC' and 'FIT' (See comments for connection)
16 - Clarifies that previous husband beats (8) - EXPOUNDS {EX}{POUNDS}
18 - Could one tirade be this with energy? Possibly (8) - DIATRIBE Anno pending. Something amiss here
20 - One may do crude work (6) - OILMAN [CD]
22 - See 4
23 - Extremely strong chap unknown to hit the books (5) - STUDY {STUD}{Y}