Acheson working with this "Big Three"? It's ancient history (7)
ACHESONTRINITY* = ANCIENTHISTORY
Dean Acheson, Truman's Secretary of State, key player in beginnings of the Marshall Plan and NATO. Straining historical accuracy slightly as he worked in the Roosevelt admin (so would have had some influence with the Stalin/Churchill/Roosevelt "Big 3") but did not have maximum influence until after Roosevelt's death.
This has been today's History Minute.