Possible Clues:

• '60s United Nations secretary general
• '60s UN head
• '60s UN leader
• U.N. V.I.P., once
• Kurt Waldheim's predecessor
• Secretary-general of the UN from 1961 to 1971
• Secretary General before Kurt Waldheim
• Buddhist who led the U.N.
• World leader elected in 1961
• Hammarskjold's successor