Just, unbiased (4)
I believe the answer is:
fair
I believe this clue is a double definition.
'just' is the first definition.
(just can mean fair in the sense of showing justice)
'unbiased' is the second definition.
(similar in meaning)
(Other definitions for fair that I've seen before include "Considerable" , "(Of skin) pale" , "Unbiased; carnival" , "Just - swings and roundabouts" , "Women are known as the ... sex" .)