Not all of total, say (4)
I believe the answer is:
some
'not all of' is the definition.
('some' is the opposite to 'all of')
'total say' is the wordplay.
'total' becomes 'sum' ('sum' can be a synonym of 'total').
'say' indicates a 'sounds like' (homophone) clue.
'sum' sounds like 'SOME'.
(Other definitions for some that I've seen before include "Several" , "Undefined number" , "certain" , "Hard work" , "An unspecified quantity, not all" .)