Medical practitioner (6)
'medical practitioner' is the definition.
(doctor is a kind of medical practitioner)
This is all the clue.
(Other definitions for doctor that I've seen before include "Who, for example" , "Tamper with - falsify - one of the 14 films" , "Medical worker or holder of highest university degree" , "Medical specialist" , "19 [WHO] , say" .)
(Other definitions for medico that I've seen before include "Health practitioner" , "quack" , "Doctor" .)
(Other definitions for physician that I've seen before include "A doctor, as in ''........, heal thyself''" , "Licensed medical practitioner" , "Medic" .)
(Other definitions for surgeon that I've seen before include "Doctor in the navy" , "Man with knife" , "Medical man" , "Medical practitioner - go nurse (anag)" , "Doctor in operating theatre - RN doctor" .)