Settler of disputes (7)
I believe the answer is:
arbiter
'settler of disputes' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for arbiter that I've seen before include "Someone with the power to settle the matter" , "Ref" , "One has the authority to settle disputes" , "Referee or judge of rarebit" , "He'll decide" .)