Old man catching nude show (7)
I believe the answer is:
cabaret
'show' is the definition.
(I've seen this before)
'old man catching nude' is the wordplay.
'old man' becomes 'cat' (old-fashioned informal term for a person).
'catching' indicates putting letters inside.
'nude' becomes 'bare' (I've seen this before).
'cat' placed around 'bare' is 'CABARET'.
(Other definitions for cabaret that I've seen before include "Nightclub entertainment, floor show" , "Entertainment provided in a nightclub" , "Entertainment at restaurant" , "Film set in 1931 Berlin - floor show" , "Musical - nightclub entertainment" .)