Arbitrator set up duty list the same (8)
I believe the answer is:
mediator
'arbitrator' is the definition.
(I've seen this before)
'set up duty list the same' is the wordplay.
'set up' shows that the letters should be reversed in order (in a down clue, letters go up).
'duty list' becomes 'rota' (I've seen this before).
'the same' becomes 'idem' (Latin for 'the same', used in citations).
'rota'+'idem'='rotaidem'
'rotaidem' back-to-front is 'MEDIATOR'.
(Other definitions for mediator that I've seen before include "One seeking to reconcile opponents" , "peacemaker" , "One intervening to settle a dispute" , "referee" , "Kind of arbitrator - one to admire" .)