Belly up (8)
'belly up' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for supine that I've seen before include "looking up" , "Recumbent" , "Flat on one's back" , "Prostrate" , "Lying face upward" .)
(Other definitions for bankrupt that I've seen before include "Insolvent debtor" , "on the rocks" , "With no redeeming qualities" , "Gone bust in business" , "Failed" .)