Cold War power, for short (4)
I believe the answer is:
ussr
(Other definitions for ussr that I've seen before include "Former federation of Russial and other states" , "Former union of socialist republics" , "In brief, former Soviet federation" , "Country established in1922 and dissolved in 1991, in short" , "Country established in 1922 and dissolved in 1991, in short" .)