Chant monotonously (6)
I believe the answer is:
intone
'chant monotonously' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for intone that I've seen before include "Recite as a chant" , "Sing (prayer) on one note" , "Recite without inflection" , "Recite with little variation in pitch" , "Speak in chant or drone" .)