Object when bird is taken in by doctor (5)
I believe the answer is:
demur
'object' is the definition.
(to demur is to object to something)
'bird is taken in by doctor' is the wordplay.
'bird' becomes 'emu' (emu is a type of bird).
'is taken in by' is an insertion indicator.
'doctor' becomes 'dr' (abbreviation).
'emu' placed inside 'dr' is 'DEMUR'.
'when' acts as a link.
(Other definitions for demur that I've seen before include "Object gently" , "Hesitate from uncertainty or object" , "Politely disagree" , "Protest mildly, show reluctance" , "Raise objections" .)