Slid off covers (4)
I believe the answer is:
lids
'covers' is the definition.
(lid is a kind of cover)
'slid off' is the wordplay.
'off' indicates anagramming the letters.
'slid' is an anagram of 'LIDS'.
(Other definitions for lids that I've seen before include "Covers for opening and closing" , "Eye covers" , "Movable tops or covers" .)