Past plump (5)
I believe the answer is:
obese
'past plump' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for obese that I've seen before include "Morbidly fat" , "Extremely portly" , "Roly-poly" , "getting well-upholstered" , "Unhealthily large" .)