Large and plump (6)
I believe the answer is:
rotund
'large and plump' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rotund that I've seen before include "'Corpulent, round (6)'" , "Round and plump" , "Portly" , "Rather obese" , "Grandiloquent; podgy" .)