Flip cover that's slippery (3)
I believe the answer is:
eel
'that's slippery' is the definition.
I can't judge whether this defines the answer.
'flip cover' is the wordplay.
'flip' says the letters should be written backwards (the order is flipped over).
'cover' becomes 'lee' (I've seen this in other clues).
'lee' backwards is 'EEL'.
Can you help me to learn more?
(Other definitions for eel that I've seen before include "User of electric organ" , "Slithery fish" , "Slippery type" , "Almost scaleless fish" , "Unagi, in a sushi bar" .)