Squiggly swimmers (4)
I believe the answer is:
eels
'squiggly swimmers' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eels that I've seen before include "Slender fish" , "Anguillae" , "Congers" , "Sea snakes among lees" , "Snakelike fish" .)