One could deal with canine -- it's barking in depression (7)
I believe the answer is:
dentist
'one could deal with canine' is the definition.
(canine is a type of tooth)
'it's barking in depression' is the wordplay.
'barking' indicates anagramming the letters (UK slang for mad).
'in' indicates putting letters inside.
'depression' becomes 'dent' (synonyms).
'its' with letters rearranged gives 'tis'.
'tis' inserted inside 'dent' is 'DENTIST'.
(Other definitions for dentist that I've seen before include "Practitioner who looks down in the mouth?" , "One who treats teeth" , "Treatment provider for teeth" , "Stinted (anag.)" , "Professional practioner" .)