Vacillates (5)
(Other definitions for dithers that I've seen before include "Flaps, wavers" , "Hesitates indecisively" .)
(Another definition for yoyos that I've seen is " Toys".)
'vacillates' is the definition.
('waver' can be a synonym of 'vacillate')
This is all the clue.
(Other definitions for wavers that I've seen before include "Dithers" , "Vacillates" .)