Sacred music from the prairies concerning God, primarily (9)
I believe the answer is:
plainsong
'sacred music' is the definition.
(I've seen this before)
'prairies concerning god primarily' is the wordplay.
'prairies' becomes 'plains' (I've seen this before).
'concerning' becomes 'on' (both can mean 'in relation to').
'primarily' says to take the initial letters.
The first letter of 'god' is 'g'.
'plains'+'on'+'g'='PLAINSONG'
'from the' is the link.
(Other definitions for plainsong that I've seen before include "church melody" , "Liturgical chant" , "Lied, perhaps" , "Mediaeval church music" , "Simple melody" .)