Diocese head (6)
I believe the answer is:
bishop
'diocese head' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bishop that I've seen before include "Man with a position on board" , "High-ranking clergyman" , "Chess piece; mulled wine" , "Head of a diocese" , "He wears the mitre and carries the crozier" .)