Fault-finding doctor is on course (10)
I believe the answer is:
censorious
'fault-finding' is the definition.
(I've seen this before)
'doctor is on course' is the wordplay.
'doctor' indicates an anagram.
'is'+'on'+'course'='isoncourse'
'isoncourse' anagrammed gives 'CENSORIOUS'.
(Other definitions for censorious that I've seen before include "Fault-finding" , "making moral judgments?" , "Severely critical" , "Blaming" .)