Ten entering to attack church officer (6)
I believe the answer is:
sexton
'church officer' is the definition.
(sexton is a kind of church officer)
'ten entering to attack' is the wordplay.
'ten' becomes 'x' (roman numeral).
'entering' indicates putting letters inside.
'to attack' becomes 'seton' ('set on' can be a synonym of 'attack'**).
'x' going within 'seton' is 'SEXTON'.
(Other definitions for sexton that I've seen before include "Graveyard employee" , "Person who tends a church and churchyard" , "One looks after church and churchyard" , "Church official" , "Church employee" .)