Old soldier and I might treat SEALs (3)

I believe the answer is:

vet

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'old soldier' is the definition.
(veteran)

I can't explain the remainder of the clue.

(Other definitions for vet that I've seen before include "Examine, check" , "Scrutinise" , "solider once" , "Examine carefully - might one help a lame duck?" , "Dog doc?" .)

I've seen this clue in The Independent.

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