Vigorous blow catching a protruding stomach (6)
I believe the answer is:
paunch
'protruding stomach' is the definition.
(I've seen this before)
'vigorous blow catching a' is the wordplay.
'vigorous blow' becomes 'punch' (I've seen this before).
'catching' means one lot of letters goes inside another.
'punch' enclosing 'a' is 'PAUNCH'.
(Other definitions for paunch that I've seen before include "Fat belly" , "Gut" , "Protuberant belly" , "Beer-belly" , "Protruding stomach" .)