Covers pimple over (4)
I believe the answer is:
tops
'covers' is the definition.
(topping is a kind of covering)
'pimple over' is the wordplay.
'pimple' becomes 'spot' (I've seen this before).
'over' is a reversal indicator.
'spot' back-to-front is 'TOPS'.
(Other definitions for tops that I've seen before include "Surpasses; toys" , "Excellent" , "First-class" , "The Four -, Motown group" , "Upper garments" .)