Finding stray cat with grin (7)
I believe the answer is:
tracing
'finding' is the definition.
(I've seen this before)
'stray cat with grin' is the wordplay.
'stray' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'cat' put after 'grin' is 'grincat'.
'grincat' with letters rearranged gives 'TRACING'.
(Other definitions for tracing that I've seen before include "produce copy?" , "Hunting down" , "design" , "Tracking or outlining on transparent paper" , "Finding by investigation" .)