Debacle — fine one as company goes under (6)
I believe the answer is:
fiasco
'debacle' is the definition.
(I know that debacle can be written as fiasco)
'fine one as company goes under' is the wordplay.
'fine' becomes 'f' (abbreviation e.g. condition of old coins, books).
'one' becomes 'i' (Roman numeral).
'company' becomes 'co' (abbreviation).
'goes under' says to put letters next to each other.
'f'+'i'+'as'+'co'='FIASCO'
(Other definitions for fiasco that I've seen before include "An utter mess or cock-up" , "Complete and utter failure" , "Sudden total disaster" , "Ignominious failure" , "A debacle, complete mess" .)