Incantatory song (5)
I believe the answer is:
chant
'incantatory song' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for chant that I've seen before include "Repetitive song" , "Repetitious sung slogan" , "Mantra" , "A monotonous song or rhythmic call" , "Repeated rhythmic song" .)