Note from the doctor accepting the compiler is up (4)
I believe the answer is:
memo
'note' is the definition.
(memo is a kind of note)
'the doctor accepting the compiler is up' is the wordplay.
'the doctor' becomes 'mo' (medical officer**).
'accepting' indicates putting letters inside.
'the compiler' becomes 'me' (the person who is writing these clues).
'is up' says the letters should be written backwards (in down clue: letters go upwards).
'me' backwards is 'em'.
'mo' going around 'em' is 'MEMO'.
'from' is the link.
(Other definitions for memo that I've seen before include "Reminder (abbr)" , "- Currie, Br. politician" , "Inter-office note" , "A brief record of events" , "Office note" .)