Communist state (4)
I believe the answer is:
ussr
'communist state' is the definition.
(I know that USSR is a communist state)
This is the entire clue.
(Other definitions for ussr that I've seen before include "Former union of socialist republics" , "The Beatles? song 'Back in the . . . .'" , "Former federation of Russial and other states" , "Country established in 1922 and dissolved in 1991, in short" , "Former Soviet Union" .)