Ham is finished and cat is upset (7)
I believe the answer is:
overact
'ham' is the definition.
('overact' can be a synonym of 'ham')
'finished and cat is upset' is the wordplay.
'finished' becomes 'over' ('over' can be similar in meaning to 'finished').
'and' means one lot of letters go next to another.
'is upset' 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 "Perform hammily" , "Do what ham thespian does" , "Exaggeratedly perform a role" , "behave exaggeratedly" , "Ham (on stage)" .)