Diplomatic representative of the Pope (6)
I believe the answer is:
nuncio
'diplomatic representative of the pope' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nuncio that I've seen before include "Sent by the Pope" , "Papal messenger" , "Diplomatic representative of the Pope" , "Papal emissary" , "Pope's ambassador" .)