It's just not raining (4)
I believe the answer is:
fair
'it's just' is the definition.
(just can mean fair in the sense of showing justice)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for fair that I've seen before include "Free from bias" , "Reasonable; pretty" , "Just treatment of others" , "[OPPOSITE OF] Dark" , "kind of entertainment" .)