Banning of former contact (15)
I believe the answer is:
excommunication
'banning' is the definition.
'former contact' is the wordplay.
'former' becomes 'ex'.
'contact' becomes 'communication'.
'ex'+'communication'='EXCOMMUNICATION'
'of' is the link.
(Other definitions for excommunication that I've seen before include "Ban" , "expulsion from church" , "Exclusion from the church" , "Strong sentence" .)