Ham is finished and cat worried (7)
I believe the answer is:
overact
'ham' is the definition.
('overact' can be a synonym of 'ham')
'finished and cat worried' is the wordplay.
'finished' becomes 'over' ('over' can be similar in meaning to 'finished').
'and' is a charade indicator (letters next to each other).
'worried' indicates an anagram.
'cat' is an anagram of 'act'.
'over'+'act'='OVERACT'
'is' acts as a link.
(Other definitions for overact that I've seen before include "Don't expect Oscar" , "behave exaggeratedly" , "Be unsubtle on stage" , "Exaggeratedly perform a role" , "Perform in an exaggerated manner" .)