Credit is doubled for emergency (6)
I believe the answer is:
crisis
'emergency' is the definition.
(a crisis is an emergency)
'credit is doubled' is the wordplay.
'credit' becomes 'cr' (abbreviation).
'doubled' indicates the doubling of some letters.
'is' duplicated is 'isis'.
'cr'+'isis'='CRISIS'
'for' is the link.
(Other definitions for crisis that I've seen before include "Serious or crucial situation" , "Decisive moment, turning point" , "Desperate situation" , "Turning point in disease" , "Turning point or crux" .)