Part the cad needed to play (6)
I believe the answer is:
detach
'part' is the definition.
(I know that detach is a more specific form of the action part)
'the cad needed to play' is the wordplay.
'needed' is a charade indicator (letters next to each other).
'to play' indicates an anagram.
'the'+'cad'='thecad'
'thecad' anagrammed gives 'DETACH'.
(Other definitions for detach that I've seen before include "Disengage (something) and remove it" , "Remove from something else, say a coupon" , "Separate one part from another" , "free" , "Separate, disconnect" .)