Bears' bellies (8)
I believe the answer is:
stomachs
I believe this clue is a double definition.
'bears'' is the first definition.
('stomach' can be a synonym of 'bear')
'bellies' is the second definition.
(I've seen this in another clue)
(Other definitions for stomachs that I've seen before include "bibles, for example" , "Four of these for bulls" , "Endures or tolerates - in abdomen?" , "Saclike organs of the body" , "They connect the oesophagus to the small intestine" .)