Complete and utter failure (6)
I believe the answer is:
fiasco
'complete and utter failure' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for fiasco that I've seen before include "Utter failure, debacle" , "Embarrassing failure" , "Ignominious failure" , "A ludicrous or humiliating failure, complete mess" , "Complete and utter failure" .)