Fairness (6)
I believe the answer is:
equity
'fairness' is the definition.
(I know that fairness can be written as equity)
This is all the clue.
(Other definitions for equity that I've seen before include "actors' group" , "Value of a property less debt" , "Moral justice for the actor's union" , "One trade union" , "Fairness or impartiality" .)