Stomach final word about bachelor party (7)
I believe the answer is:
abdomen
'stomach' is the definition.
(synonyms)
'final word about bachelor party' is the wordplay.
'final word' becomes 'amen' (I've seen this before).
'about' indicates putting letters inside.
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'party' becomes 'do' (do is a kind of party).
'b'+'do'='bdo'
'amen' placed around 'bdo' is 'ABDOMEN'.
(Other definitions for abdomen that I've seen before include "Central region" , "guts" , "Site of corporation" , "gut" , "Tummy" .)