Arbitrator acceptable for head of large organisation (6)
I believe the answer is:
umpire
'arbitrator' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for umpire that I've seen before include "The ref in cricket match" , "Arbiter of cricket match" , "One enforcing the rules in games" , "Arbitrator (in certain sports)" , "Impure (anag) - adjudicator" .)