Unaccompanied church music sung in unison — a ninth clap (anag) (10)
I believe the answer is:
plainchant
(Other definitions for plainchant that I've seen before include "form of sacred music" , "unison singing" .)
I've seen this clue in The Guardian.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free.
Check out my app
or
learn more
about the Crossword Genius project.