Average portion of miso soup (2-2)
I believe the answer is:
so-so
'average' is the definition.
(I've seen this before)
'portion of miso soup' is the wordplay.
'portion of' says the answer is hidden in the clue.
'SO-SO' is hidden within 'miso soup'.
(Other definitions for so-so that I've seen before include "Informally, only moderately good or well" , "Of average quality" , "Rather middling" , "OK, but nothing special" , "Neither good nor bad" .)