Credit is doubled -- catastrophe! (6)
I believe the answer is:
crisis
'catastrophe' is the definition.
(thesaurus)
'credit is doubled' is the wordplay.
'credit' becomes 'cr' (abbreviation).
'doubled' indicates the doubling of some letters.
'is' duplicated is 'isis'.
'cr'+'isis'='CRISIS'
(Other definitions for crisis that I've seen before include "Emergency - decision time" , "Crucial or decisive moment" , "Moment of danger" , "unstable period" , "Decisive or critical moment" .)