The intestine (or belly) (3)
I believe the answer is:
gut
I believe this is a double definition.
'the intestine' is the first definition.
(synonyms)
'belly' is the second definition.
(informal term for the stomach or gut)
(Other definitions for gut that I've seen before include "Part of the alimentary canal" , "Natural violin string material" , "one's bust in strenuous effort" , "Rip out (a place's) interior" , "Empty" .)