Cream-covered bun or tart (7)
I believe the answer is:
trollop
'tart' is the definition.
('trollop' can be a synonym of 'tart')
'cream-covered bun' is the wordplay.
I cannot really understand how this works, but
'bun' could be 'roll' ('roll' can be a synonym of 'bun') and 'roll' is found within the answer.
The remaining letters 'top' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'or' is the link.
Can you help me to learn more?
(Other definitions for trollop that I've seen before include "loose woman" , "Promiscuous woman" , "Prostitute" , "Disreputable woman" , "Baggage" .)