Fellow worshippers, say, participating in sombre threnody (8)
I believe the answer is:
brethren
'fellow worshippers' is the definition.
The answer and definition can be both people as well as being plural nouns.
Maybe there's a link between them I don't understand?
'participating in sombre threnody' is the wordplay.
'participating in' indicates the answer is hidden within the clue.
'BRETHREN' is hidden in the letters of 'sombre threnody'.
'say' is the link.
Can you help me to learn more?
(Other definitions for brethren that I've seen before include "monks" , "Brotherhood" , "Fellow male members" , "See 12" , "old relatives?" .)