Stout belly surprisingly empty (5)
I believe the answer is:
gutsy
'stout' is the definition.
(thesaurus)
'belly surprisingly empty' is the wordplay.
'belly' becomes 'gut' (informal term for the stomach or gut).
'empty' says to hollow out the word (remove centre letters).
'surprisingly' with its middle taken out is 'sy'.
'gut'+'sy'='GUTSY'
(Other definitions for gutsy that I've seen before include "Being full of courage" , "Sort of (non-standard)" , "Bold" , "Plucky" , "Spirited; greedy" .)