Fellow novice ultimately left church (6)
I believe the answer is:
chapel
'church' is the definition.
(I know that chapel is a type of church)
'fellow novice ultimately left' is the wordplay.
'fellow' becomes 'chap' (both can mean a man).
'ultimately' indicates one should take the final letters.
'left' becomes 'l' (common abbreviation).
The last letter of 'novice' is 'e'.
'chap'+'e'+'l'='CHAPEL'
(Other definitions for chapel that I've seen before include "Perhaps part of cathedral" , "Place of worship with an altar" , "Branch of a newspaper trade union" , "Place of worship set apart in church or cathedral" , "union group" .)