Doctor quit or is at home before examiner (10)
I believe the answer is:
inquisitor
'examiner' is the definition.
(I have seen 'Ruthless examiner' mean 'inquisitor' so perhaps 'examiner' could also mean 'inquisitor')
'doctor quit or is at home before' is the wordplay.
'doctor' indicates anagramming the letters.
'at home' becomes 'in' (similar in meaning).
'before' is a charade indicator (letters next to each other).
'quit'+'or'+'is'='quitoris'
'quitoris' anagrammed gives 'quisitor'.
'quisitor' put after 'in' is 'INQUISITOR'.
(Other definitions for inquisitor that I've seen before include "One prize crossword" , "One questions" , "Investigator, examiner" , "Harsh questioner" , "Ruthless examiner" .)