Small whirlpool (4)
'small whirlpool' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eddy that I've seen before include "Small circular movement of water" , "Founder of Christian Science, d. 1910" , "Whirl (in fluid)" , "Swirl; small whirlpool" , "religious leader" .)