Racetrack doc (3)
I believe the answer is:
vet
'racetrack doc' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for vet that I've seen before include "Scrutinise" , "Experienced" , "Critically examine" , "'Examine this doctor, in short (3)'" , "'Animal doctor, in short (3)'" .)