Son puts identifying labels on animals (5)

I believe the answer is:

stags

'animals' is the definition.
(stag is a kind of animal)

'son puts identifying labels on' is the wordplay.
'son' becomes 's'.
'puts identifying labels on' becomes 'tags' (to tag something is to label it).
's'+'tags'='STAGS'

(Another definition for stags that I've seen is " Male deer".)

I've seen this clue in The Telegraph.

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