Just (4)
'just' is the definition.
(just can mean fair in the sense of showing justice)
This is all the clue.
(Other definitions for fair that I've seen before include "Market for the sale of produce" , "not cloudy" , "(Of weather) fine and dry" , "Just; passable" , "Reasonable target?" .)
'just' is the definition.
('just' can mean 'mere' or 'only')
This is the entire clue.
(Other definitions for mere that I've seen before include "Unimpressive" , "Lake, pond (poetic)" , "a drop of water" , "Nothing more than what is specified (4)" , "Nothing more than is specified - or a poetic lake" .)
'just' is the definition.
(I know that just can be written as only)
This is all the clue.
(Other definitions for only that I've seen before include "Unique; merely" , "See 6" , "Exclusive - individual" , "Mere" , ". . . . the Lonely (sung by Roy Orbison)" .)
'just' is the definition.
(barely can mean only just)
This is all the clue.
(Other definitions for barely that I've seen before include "how naturists exist" , "Not quite" , "just a short while before" , "how babies are born?" , "By a small margin" .)
'just' is the definition.
(I know that just can be written as merely)
This is all the clue.
(Other definitions for merely that I've seen before include "'Only, and nothing more (6)'" , "Just one" , "Simply - only" .)
'just' is the definition.
(solely means just or only)
This is the entire clue.
(Other definitions for solely that I've seen before include "Singly" , "Exclusively, only" , "nowhere else?" , "Singularly" , "alone" .)
'just' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for rightful that I've seen before include "Legitimate, fitting" , "Lawful" , "Legitimately claimed" , "Proper - legitimate" , "Legally valid" .)