Stuff stomach, say, and go belly up (8)
I believe the answer is:
organdie
'stuff' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'stomach say and go belly up' is the wordplay.
'stomach say' becomes 'organ' (stomach is a kind of organ).
'and' is a charade indicator (letters next to each other).
'go belly up' becomes 'die' (I can't explain this - if you can you should give a lot more credence to this answer).
'organ'+'die'='ORGANDIE'
Can you help me to learn more?
(Other definitions for organdie that I've seen before include "Fine stiffened translucent fabric" , "A stiffened muslin; I groaned (anag.)" , "I groaned about translucent fabric" , "Fine material" , "Orange I'd changed for fine muslin" .)