Man in charge, supported by a church (8)
I believe the answer is:
basilica
'church' is the definition.
(basilica is a kind of church)
'man in charge supported by a' is the wordplay.
'man' becomes 'basil' (I've seen this before**).
'in charge' becomes 'ic'.
'supported by' says to put letters next to each other (letters go below - in down clue).
'basil'+'ic'+'a'='BASILICA'
(Other definitions for basilica that I've seen before include "A large Christian church with two rows of columns (8)" , "Large (Roman Catholic) church" , "Important Roman Catholic church" , "Form of church building" , "Large church building" .)