Setter perhaps is to make good (3)
I believe the answer is:
dog
'setter perhaps' is the definition.
(setter is a kind of dog)
'make good' is the wordplay.
'make' becomes 'do' (doing is a kind of making).
'good' becomes 'g' (abbreviation).
'do'+'g'='DOG'
'is to' acts as a link.
(Other definitions for dog that I've seen before include "Contemptible man" , "plague?" , "'Every ... is allowed one bite'" , "Follow; pet" , "Lassie" .)