After a party, a mother is a state! (7)
I believe the answer is:
alabama
'a state' is the definition.
(Alabama is an example)
'after a party a mother' is the wordplay.
'after' means one lot of letters go next to another.
'party' becomes 'lab' (abbreviation for Labour**).
'mother' becomes 'ma' (ma is a kind of mother).
'a' next to 'lab' is 'alab'.
'alab'+'a'+'ma'='ALABAMA'
'is' is the link.
(Other definitions for alabama that I've seen before include "part of US" , "US state west of Georgia" , "State of SE USA" , "US state in which Birmingham is situated" , "US state on the Gulf of Mexico" .)