Buxom partner getting caught on top (6)
I believe the answer is:
chubby
'buxom' is the definition.
('chubby' can be a synonym of 'buxom')
'partner getting caught on top' is the wordplay.
'partner' becomes 'hubby' (hubby is a kind of partner).
'getting caught' becomes 'c' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on top' says to put letters next to each other (down clues only).
'hubby' after 'c' is 'CHUBBY'.
(Other definitions for chubby that I've seen before include "Fat in the face" , "Plumb and round" , "On the plump side" , "Plump, rounded" , "with some corporation?" .)