Head-moving approval (3)
I believe the answer is:
nod
'head-moving approval' 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 "drift" , "It's said to be as good as a wink" , "Doze" , "'A . . . is as good as a wink to a blind horse'" , "OK" .)