Papal representative (6)
(Other definitions for nuncio that I've seen before include "Vatican delegate" , "Sent by the Pope" , "Papal diplomat" , "Papal emissary" , "Papal messenger" .)
'papal representative' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for legate that I've seen before include "One being tested" , "Papal envoy from Galtee" , "Vatican emissary" , "papal emissary" , "Envoy, maybe papal" .)