Financial backer to support a run on church port (9)
I believe the answer is:
archangel
'port' is the definition.
(city and port in Archangelsk oblast, Russia)
'financial backer to support a run on church' is the wordplay.
'financial backer' becomes 'angel' (I've seen this before).
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'a run' becomes 'ar' (I've seen this in other clues**).
'on' is a charade indicator (letters next to each other).
'church' becomes 'ch' (common abbreviation).
'ar'+'ch'='arch'
'angel' put after 'arch' is 'ARCHANGEL'.
(Other definitions for archangel that I've seen before include "foreign port" , "Russian port on the White Sea" , "celestial flier" , "Most important of divine messengers" , "Highest ranking member of the celestial hierarchy" .)