Having nothing in belly causes disease (4)
I believe the answer is:
gout
'disease' is the definition.
(gout is a kind of disease)
'having nothing in belly' is the wordplay.
I cannot quite understand how this works, but
'nothing' could be 'o' (looks like zero - 0) and 'o' is found in the answer.
'belly' could be 'gut' (informal term for the stomach or gut) and 'gut' is present in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'causes' is the link.
Can you help me to learn more?
(Other definitions for gout that I've seen before include "Disease affecting joints" , "Painful inflammation of the big toe" , "Disease caused by excess uric acid in the bloodstream" , "Disease inflaming the big toe" , "Painful inflammation of the foot" .)