Doctor tries another examination (5)
I believe the answer is:
resit
'another examination' is the definition.
(another attempt at sitting an exam)
'doctor tries' is the wordplay.
'doctor' is an anagram indicator.
'tries' anagrammed gives 'RESIT'.
(Other definitions for resit that I've seen before include "take another exam" , "second try at test" , "repeated test" , "Take examination again" , "Retake exam" .)