Does he appear in a musical? (6)
I believe the answer is:
cheats
'does he' is the definition.
The definition suggests a singular noun but the answer is a plural noun.
'appear in a musical?' is the wordplay.
'appear' becomes 'he' (I can't justify this - if you can you should believe this answer much more).
'in' is an insertion indicator.
'a musical?' becomes 'cats' (I've seen this before).
'he' going within 'cats' is 'CHEATS'.
Can you help me to learn more?
(Other definitions for cheats that I've seen before include "Doesn't follow the rules of the game" , "Swindles or deceives as at cards" , "Swindles in chaste manner" , "Deceivers" , "Acts dishonestly, perhaps in card game" .)