Not all a resting actor needs (4)
I believe the answer is:
part
'not all' is the definition.
('part' is the opposite to 'all')
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for part that I've seen before include "Piece, segment" , "Piece; divide" , "Sever; portion" , "Constituent - something to play?" , "Portion, segment" .)