Puffs up (6)
I believe the answer is:
swells
'puffs up' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for swells that I've seen before include "Informally posh people" , "Grows larger like posh people" , "Becomes larger in size for posh people" , "VIPs" , "BEcomes larger in volume, size or intensity" .)