It's only fair (4)

I believe the answer is:

just

This clue is a double definition.

'it's only' is the first definition.
('just' can be a synonym of 'only')

'fair' is the second definition.
('just' can be a synonym of 'fair')

(Other definitions for just that I've seen before include "legal?" , "By a whisker" , "Barely - equitable" , "Simply - fair" , "Recently" .)

I've seen this clue in The Telegraph and The Globe and Mail.

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