Exhausted hosting a church wedding (8)
I believe the answer is:
alliance
'wedding' is the definition.
(thesaurus)
'exhausted hosting a church' is the wordplay.
'exhausted' becomes 'all in' ('all in' can mean exhausted).
'hosting' is an insertion indicator (inserted letters are welcomed in or hosted).
'church' becomes 'CE' (abbreviation for Church of England).
'allin' enclosing 'a' is 'allian'.
'allian'+'ce'='ALLIANCE'
(Other definitions for alliance that I've seen before include "The joining by political agreement or treaty" , "Kind of partnership with canaille" , "match?" , "A joining of forces" , "Bond" .)