One examines canines first after depression (7)
I believe the answer is:
dentist
'one examines canines' is the definition.
(canine is a type of tooth)
'first after depression' is the wordplay.
'first' becomes 'ist' (ist resembles dst).
'after' says to put letters next to each other.
'depression' becomes 'dent' (synonyms).
'ist' after 'dent' is 'DENTIST'.
(Other definitions for dentist that I've seen before include "Tooth surgeon" , "Teeth treater" , "Someone who drills for a living?" , "Tooth expert" , "Tooth doctor" .)