All or just part, say (3)
I believe the answer is:
sum
'all' is the definition.
(I've seen this before)
'part say' is the wordplay.
'part' becomes 'some' (I've seen this before).
'say' shows a homophone (sound like).
'some' is a homophone of 'SUM'.
'or just' acts as a link.
(Other definitions for sum that I've seen before include "Mathematical problem" , "Quantity obtained by addition" , "Whole" , "Quantity of money" , "pupils find it a problem" .)