One involved in canine welfare? (7)

I believe the answer is:

dentist

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'one involved in canine welfare?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

This is the entire clue.

Can you help me to learn more?

(Other definitions for dentist that I've seen before include "Teeth specialist" , "Professional practioner" , "Person qualified to treat teeth - tends it (anag)" , "Teeth treater" , "Tooth surgeon" .)

I've seen this clue in The Independent.

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