Covers over notice (4)
I believe the answer is:
spot
'notice' is the definition.
(I've seen this before)
'covers over' is the wordplay.
'covers' becomes 'tops' (topping is a kind of covering).
'over' says the letters should be written backwards.
'tops' in reverse letter order is 'SPOT'.
(Other definitions for spot that I've seen before include "Notice - fictional puppy" , "See; round mark" , "Catch sight of mark in pots" , "Pimple; place" , "station" .)