Tacit assents (4)
I believe the answer is:
nods
'tacit 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 about to crash?" , "Indicates assent" , "Non-verbal indications of assent" , "Inclines head" , "Is careless" .)