Belly shown by sailor attending party with soldiers (7)
I believe the answer is:
abdomen
'belly' is the definition.
(synonyms)
'sailor attending party with soldiers' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'attending' means one lot of letters go next to another.
'party' becomes 'do' (do is a kind of party).
'with' is a charade indicator (letters next to each other).
'soldiers' becomes 'men' (men can mean a group of soldiers).
'ab'+'do'+'men'='ABDOMEN'
'shown by' is the link.
(Other definitions for abdomen that I've seen before include "Midriff" , "Ban demo (anag)" , "Part of body containing the digestive organs" , "Site of corporation" , "pot" .)