Swing wildly (5)
I believe the answer is:
flail
'swing wildly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for flail that I've seen before include "Thresher; wave helplessly about" , "thrash around" , "Wave about wildly" , "Old tool for threshing grain" , "Threshing implement" .)