1560s, "action of clearing," from clear (v.) + -ance. Meaning "a clear space" is from 1788. Meaning "approval, permission" (especially to land or take off an aircraft) is from 1944, American English; national security sense recorded from 1948. Clearance sale attested by 1843.
实用例句
1. The UN pledged to help supervise the clearance of mines.
联合国承诺协助监督扫雷工作。
来自柯林斯例句
2. They have to wait for clearance from air traffic control.
他们需要等空中交通管制人员的放行。
来自柯林斯例句
3. He has a security clearance that allows him access to classified information.
他获得了安全许可，可以接触机密信息。
来自柯林斯例句
4. Thai Airways said the plane had been given clearance to land.
