Vibrates (6)
I believe the answer is:
shakes
'vibrates' is the definition.
(shaking is a kind of vibrating)
This is the entire clue.
(Other definitions for shakes that I've seen before include "Moves quickly up and down, say milk drink" , "Judders" , "jars" , "Quivers" , "Frothy drink of milk and flavouring" .)