Odd fish found in the lees (4)
I believe the answer is:
eels
'odd fish found in the lees' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for eels that I've seen before include "Elongated fishes" , "Anguillae" , "Slippery creatures" , "Long, fleshy fish" , "Else they're fish" .)