Congregation to collapse (4)
I believe the answer is:
fold
I believe this clue is a double definition.
'congregation' is the first definition.
(as in welcoming someone into 'the fold')
'collapse' is the second definition.
(as in a business folding)
'to' is the link.
(Other definitions for fold that I've seen before include "close" , "Collapse; bend in half" , "go bankrupt, perhaps" , "Crease" , "Cease trading" .)