Christian messenger (7)
I believe the answer is:
apostle
'christian messenger' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for apostle that I've seen before include "To lapse (anag) - ardent supporter of a cause" , "Principal champion" , "Augustine, say" , "Chosen disciple" , "Preacher perhaps" .)