Arbitrator made it complex, in other words (8)
I believe the answer is:
mediator
'arbitrator' is the definition.
(thesaurus)
'made it complex in other words' is the wordplay.
'complex' indicates an anagram.
'in other words' becomes 'or' (I've seen this in other clues).
'made'+'it'='madeit'
'madeit' anagrammed gives 'mediat'.
'mediat'+'or'='MEDIATOR'
(Other definitions for mediator that I've seen before include "Negotiator between opposing parties" , "One intervening to settle a dispute" , "An honest broker" , "One seeking to reconcile opponents" , "Kind of arbitrator - one to admire" .)