Unagi on a sushi menu (3)
I believe the answer is:
eel
'unagi on a sushi menu' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eel that I've seen before include "Evasive type" , "Slippery creature" , "A sea snake" , "slipper" , "Wriggly fish" .)