Simply fair (4)
I believe the answer is:
just
I believe this clue is a double definition.
'simply' is the first definition.
('just' can be a synonym of 'simply')
'fair' is the second definition.
('just' can be a synonym of 'fair')
(Other definitions for just that I've seen before include "legal?" , "Merely - fair" , "Barely honest?" , "And nothing more" , "Hardly" .)