Amelioration (6)
(Other definitions for upturn that I've seen before include "Boom after a bust" , "Recovery" , "economic improvement" , "Improved trend in business or fortune" , "Improvement, better trend in business" .)
'amelioration' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for improvement that I've seen before include "Act of making better" , "Upgrade" , "recovery" , "A change for the better" , "upgrading" .)