Round and plump, and pompous (7)
I believe the answer is:
orotund
'pompous' is the definition.
(thesaurus)
'round and plump' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'and' says to put letters next to each other.
'plump' becomes 'rotund' (I've seen this before).
'o'+'rotund'='OROTUND'
'and' acts as a link.
(Other definitions for orotund that I've seen before include "booming" , "Pompous (in style)" , "Full, clear and musical" , "Resonant" , "Full, round" .)