Head-moving assents (4)
I believe the answer is:
nods
'head-moving assents' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nods that I've seen before include "Is careless" , "gestures in agreement" , "Non-verbal indications of assent" , "Indicates assent" , "Shows assent" .)