Quite impartially (6)
I believe the answer is:
fairly
I believe this clue is a double definition.
'quite' is the first definition.
(thesaurus)
'impartially' is the second definition.
(thesaurus)
(Other definitions for fairly that I've seen before include "Evenhandedly" , "In an evenhanded manner - somewhat" , "To a moderate degree" , "Justly, without favouring one party" , "Moderately" .)