Barely impartial (4)
I believe the answer is:
just
I believe this is a double definition.
'barely' is the first definition.
(synonyms)
'impartial' is the second definition.
(associated in meaning)
(Other definitions for just that I've seen before include "Exactly" , "Morally right" , "Barely; impartial" , "Fair and proper" , "Barely; right and fair" .)