Cast top layer, staying inside (7)
I believe the answer is:
players
'cast' is the definition.
(I've seen this in another clue)
'top layer staying inside' is the wordplay.
'inside' indicates a hidden word.
'PLAYERS' is hidden within 'top layer staying'.
(Other definitions for players that I've seen before include "Performers" , "They participate in games" , "Team members" , "Actors" , "Musicians" .)