Snaky swimmer (3)
I believe the answer is:
eel
'snaky swimmer' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eel that I've seen before include "Elongated fish" , "Slippery type" , "Sea creature like conger" , "Conger, e.g." , "Teleost fish" .)