Now the religious leaders in self-help group are making natural bone cavities? (5)
I believe the answer is:
antra
'bone cavities?' is the definition.
(I've seen this before)
'now the religious leaders in self-help group' is the wordplay.
'leaders' suggests taking the first letters.
'in' is an insertion indicator.
'self-help group' becomes 'aa' (Alcoholics Anonymous).
The initial letters of 'now the religious' is 'ntr'.
'ntr' going into 'aa' is 'ANTRA'.
'are making natural' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for antra that I've seen before include "Natural cavities in bone; ratan (anag.)" , "Hollow spaces" , "Chambers" , "Natural hollows" , "Cave!" .)