Father's fur is fair! (8)
I believe the answer is:
passable
'is fair' is the definition.
(synonyms)
'father's fur' is the wordplay.
'father's' becomes 'pa's' (pa can mean dad or father).
'fur' becomes 'sable' (sable is a kind of fur).
'pas'+'sable'='PASSABLE'
(Other definitions for passable that I've seen before include "OK" , "okay?" , "Merely satisfactory" , "Barely adequate" , "Fair" .)