Zero for an endless composition (4)
I believe the answer is:
none
'zero' is the definition.
(I've seen this before)
'an endless composition' is the wordplay.
'an endless' means to remove the last letter.
'composition' becomes 'nonet' (I've seen this before).
'nonet' with its final letter removed is 'NONE'.
'for' is the link.
(Other definitions for none that I've seen before include "Zero" , "0?" , "Not even one" , "Not a sausage" , "hour of prayer" .)