Dog's doc (3)
I believe the answer is:
vet
'dog's 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 "'Examine this doctor, in short (3)'" , "Examine carefully for suitability" , "Old soldier (inf.)" , "Examine carefully - might one help a lame duck?" , "Experienced" .)