Sudden and ignominious failure (7)
I believe the answer is:
debacle
'sudden and ignominious failure' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for debacle that I've seen before include "Rout; fiasco" , "A sound defeat" , "Sudden and violent collapse" , "Utter failure" , "Sudden disastrous collapse or defeat" .)