Animal doctors (4)
I believe the answer is:
vets
'animal doctors' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for vets that I've seen before include "old soldiers" , "13 doctors?" , "Inspects (animals?)" , "Investigates thoroughly to ensure suitability, for a job perhaps" , "Screens for the job perhaps" .)