Old soldier possibly barked at? (3)

I believe the answer is:

vet

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'old soldier' is the definition.
(I've seen this in other clues)

I cannot understand how the rest of the clue works.

(Other definitions for vet that I've seen before include "Critically examine" , "Examine, check" , "Scrutinise" , "Old soldier (inf.)" , "Screen" .)

I've seen this clue in the Evening Standard.

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