Vet wearing glasses trimmed cat's tail (7)
I believe the answer is:
inspect
'vet' is the definition.
(I've seen this before)
'wearing glasses trimmed cat's tail' is the wordplay.
'wearing' becomes 'in' (as in being 'in' certain clothes).
'glasses' becomes 'specs' (spectacles).
'trimmed' means to remove the last letter (the final letter is trimmed off).
'tail' says to take the final letters.
The final letter of 'cat' is 't'.
'specs' with its last letter taken away is 'spec'.
'in'+'spec'+'t'='INSPECT'
(Other definitions for inspect that I've seen before include "Assess; examine" , "Scan" , "Scrutinize, audit" , "Look critically at" , "vet" .)