*Cold War barrier (4,7)
I believe the answer is:
iron curtain
'cold war barrier' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for iron curtain that I've seen before include "What divided European sides" , "Notional barrier between East and West" , "divider" , "former division in Europe" , "Impenetrable barrier" .)