Early Christian missionary (7)
I believe the answer is:
apostle
'early christian missionary' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for apostle that I've seen before include "Thaddeus, perhaps" , "Vigorous supporter" , "Leaps to find religious follower" , "[JAMES] , for one?" , "Evangelist, proponent" .)