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