Credit one's doubled creating catastrophe (6)
I believe the answer is:
crisis
'catastrophe' is the definition.
(thesaurus)
'credit one's doubled' is the wordplay.
'credit' becomes 'cr'.
'one's' becomes 'is' (roman numeral).
'doubled' indicates the doubling of some letters.
'is' duplicated is 'isis'.
'cr'+'isis'='CRISIS'
'creating' is the link.
(Other definitions for crisis that I've seen before include "Crucial point - decision time" , "Period of dire trouble" , "mess" , "a difficult situation" , "Emergency or turning point" .)