Blustering fellow's gained a little weight (5)
I believe the answer is:
gusty
'blustering' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for gusty that I've seen before include "Windy" , "Blowing intermittently" , "Of wind, blowing in bursts" .)