After prayer, regularly disowns offertory (10)
I believe the answer is:
collection
'offertory' is the definition.
(I've seen this before)
'after prayer regularly disowns' is the wordplay.
'after' says to put letters next to each other.
'prayer' becomes 'collect' (collect is a type of prayer).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'disowns' are 'ion'.
'collect' next to 'ion' is 'COLLECTION'.
(Other definitions for collection that I've seen before include "whip-round" , "Part of service" , "Group" , "Number of accumulated items" , "Offertory" .)