Wiggle (3)
I believe the answer is:
wag
'wiggle' is the definition.
(I know that wag is a more specific form of the action the wiggle)
This is all the clue.
(Other definitions for wag that I've seen before include "Joker; move tail" , "He must be joking" , "Wave to and fro, as a dog's tail" , "Comedian" , "Move briskly like dog's tail" .)