A tasteful slipper (3)

I believe the answer is:

eel

I'm a little stuck... Click here to teach me more about this clue!

'slipper' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for eel that I've seen before include "Slippery character" , "User of electric organ" , "Slippery figure" , "Slimy fish" , "Ribbon-like fish" .)

Want a hint initially instead of a full solution? Install my app