Nonverbal assent (3)
I believe the answer is:
nod
'nonverbal assent' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nod that I've seen before include "Fellow that's set up number 500" , "overlook something" , "slight bow" , "Signify assent" , "The Land of ... lay east of Eden" .)