Moray or conger (3)
I believe the answer is:
eel
I believe this is a double definition.
'moray' is the first definition.
(I've seen this in another clue)
'conger' is the second definition.
(I've seen this in another clue)
(Other definitions for eel that I've seen before include "Slippery type" , "Snaky fish" , "Slippery person" , "Creature like conger or moray" , "Slippery figure" .)