Indicate approval to drop off (3)
I believe the answer is:
nod
I believe this clue is a double definition.
'indicate approval' is the first definition.
(I've seen this in another clue)
'drop off' is the second definition.
(I've seen this in another clue)
'to' acts as a link.
(Other definitions for nod that I've seen before include "Where Cain went to" , "overlook something" , "Indicate assent; make slip" , "Show recognition" , "Gesture of acceptance" .)