Chorus having origins in religion initially (5)
I believe the answer is:
choir
'chorus' is the definition.
(choir is a kind of chorus)
'having origins in religion initially' is the wordplay.
'origins' indicates taking the first letters.
'in' is an insertion indicator.
'religion initially' becomes 'coir' (I can't explain this - if you can you should believe this answer much more).
The initial letter of 'having' is 'h'.
'h' inserted into 'coir' is 'CHOIR'.
Can you help me to learn more?
(Other definitions for choir that I've seen before include "Religious chorus, perhaps" , "Carol singers?" , "warblers" , "set of singers" , "Singers in harmony" .)