Crises one mishandled in slump (9)
I believe the answer is:
recession
'slump' is the definition.
(a recession is an economic slump)
'crises one mishandled' is the wordplay.
'mishandled' is an anagram indicator.
'crises'+'one'='crisesone'
'crisesone' is an anagram of 'RECESSION'.
'in' is the link.
(Other definitions for recession that I've seen before include "Decline in economic activity and prosperity" , "Down-turn" , "Widespread decline in employment and trade" , "Slump" , "Period of temporary economic decline" .)