Intimate former partner's heading for ban from services (13)
I believe the answer is:
excommunicate
'ban from services' is the definition.
(to excommunicate is to ban from church services)
'intimate former partner's heading' is the wordplay.
'intimate' becomes 'communicate' (intimate can mean to utter or communicate).
'former partner' becomes 'ex' (an ex-partner).
'heading' means one lot of letters go next to another (some letters go in front of or head others).
'communicate' after 'ex' is 'EXCOMMUNICATE'.
'for' acts as a link.
(Other definitions for excommunicate that I've seen before include "Cut off from church sacraments" , "Officially ban from church" , "removed from church" , "Deprive of church privileges" , "Outlaw" .)