Only fair (4)
This clue is a double definition.
'only' is the first definition.
(synonyms)
'fair?' is the second definition.
(Synonym)
(Other definitions for just that I've seen before include "By the skin of your teeth - equitable" , "Hardly" , "Fair-minded" , "Barely - deserved" , "Fair - precisely" .)
'only fair' is the definition.
(I've seen this in another clue)
This is all the clue.
(Another definition for two-star that I've seen is " At worst (anag.)".)