Somewhat ecstatic at changes in contract (5)
I believe the answer is:
catch
'contract' is the definition.
(thesaurus)
'somewhat ecstatic at changes' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'CATCH' is hidden within 'ecstatic at changes'.
'in' acts as a link.
(Other definitions for catch that I've seen before include "Arrest" , "It's taken by a fielder to dismiss a player in baseball and cricket" , "problem being concealed" , "Grab hold of - fastener" , "Getting round" .)