Nuclear restraint pact

TESTBAN

This 1963 treaty aimed to limit radioactive fallout by prohibiting detonations in the atmosphere, underwater, and in outer space. Think of its full name’s first word.

The clue "Nuclear restraint pact" refers to the Test Ban Treaty, a 1963 agreement limiting nuclear weapons testing in the atmosphere, underwater, and in outer space. The answer "TESTBAN" is a shortened form of the treaty’s name, blending "test" (as in nuclear tests) with "ban" (the restriction). It’s a straightforward definition with no wordplay—just a historical reference to a key arms control deal.