Eddy (9)
I believe the answer is:
whirlpool
'eddy' is the definition.
(I know that eddy can be written as whirlpool)
This is all the clue.
(Other definitions for whirlpool that I've seen before include "Quickly rotating mass of water" , "Violent circular eddy of water" , "Strong circular current" , "Powerful circular current of water" .)