Just not dark (4)
I believe the answer is:
fair
This might be a double definition.
'just' is the first definition.
(just can mean fair in the sense of showing justice)
'not dark' is the second definition.
Both the definition and answer are adjectives. Perhaps there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for fair that I've seen before include "Just; amusement" , "Just; beautiful; blond" , "light headed" , "[OPPOSITE OF] Dark" , "Traders' gathering" .)