Part of stomach revolting at bread (5)
I believe the answer is:
pitta
'bread' is the definition.
(I've seen this before)
'part of stomach revolting at' is the wordplay.
'part of stomach' becomes 'pit' (the pit of one's stomach).
'revolting' shows that the letters should be reversed in order.
'at' reversed gives 'ta'.
'pit'+'ta'='PITTA'
(Other definitions for pitta that I've seen before include "Greek unleavened bread" , "Type of flat bread that's split to hold a filling" , "Bread pocket" , "Type of flatbread" , "Slightly leavened bread" .)