Tornado (7)
I believe the answer is:
twister
'tornado' is the definition.
(I know that tornado can be written as twister)
This is all the clue.
(Other definitions for twister that I've seen before include "One-eyed menace" , "Tornado (American)" , "Tornado (colloq.)" , "Colloquial name for a tornado" , "Funnel-shaped wind" .)