Merely being fair (4)
I believe the answer is:
just
This clue is a double definition.
'merely' is the first definition.
('just' can be a synonym of 'merely')
'fair' is the second definition.
('just' can be a synonym of 'fair')
'being' is the link.
(Other definitions for just that I've seen before include "Exactly" , "Barely; impartial" , "Fair; a moment ago" , "Book by Richmal Crompton" , "free from bias" .)