The Beatles' "Back in the ___" (4)

I believe the answer is:

ussr

(Other definitions for ussr that I've seen before include "Former federation of Russial and other states" , "In brief, former Soviet federation" , "Former Soviet Union" , "Former union of socialist republics" , "Country established in 1922 and dissolved in 1991, in short" .)

I've seen this clue in The Wall Street Journal and the Universal.

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