名词

1. 清除;清理
Clearance is the removal of old buildings, trees, or other things that are not wanted from an area.

2. (官方的)批准，许可
If you get clearance to do or have something, you get official approval or permission to do or have it.

3. (路面、河面与上方桥梁之间的)净空，间隙，间距
The clearance of a bridge is the distance between the lowest point of the bridge and the road or the water under the bridge.

1. permission to proceed

e.g. the plane was given clearance to land

2. the distance by which one thing clears another
the space between them

3. vertical space available to allow easy passage under something

Synonym: headroomheadway