Time goes in for prince in cat costume (7)
I believe the answer is:
leotard
'costume' is the definition.
(I've seen this before)
'time goes in for prince in cat' is the wordplay.
I cannot really understand how this works, but
'time' could be 't' (abbreviation) and 't' is present in the answer.
'cat' could be 'leo' ('lion' in Latin) and 'leo' is found within the answer.
The remaining letters 'ard' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for leotard that I've seen before include "Tight-fitting garment, for gymnasts say" , "Skin-tight garment worn by acrobats" , "Garment worn by ballet dancers" , "Ballet outfit" , "Do alter the dancer's garment" .)