A portion each (6)
I believe the answer is:
apiece
'each' is the definition.
(synonyms)
'a portion' is the wordplay.
'portion' becomes 'piece' (piece is a kind of portion).
'a'+'piece'='APIECE'
(Other definitions for apiece that I've seen before include "Per person" , "For or by each one of group" , "A head" , "for everyone" .)