Intone (5)
I believe the answer is:
chant
'intone' is the definition.
(I know that intone can be written as chant)
This is all the clue.
(Other definitions for chant that I've seen before include "Sing" , "Intone (psalm)" , "Type of group singing" , "Mantra" , "Type of singing with a simple melody and several words sung on one note" .)