clearance
n. C / Un. the official permission to do something, or the space between two objects so they do not touch. It can also mean a big sale where a shop sells things at low prices to empty the shelves.
n. official authorisation for an action or access to restricted information; also, the physical gap between two objects allowing for movement. In a commercial context, it refers to the disposal of stock at reduced prices.
The pilot waited for clearance before taking off.
The truck was too tall to pass under the bridge because there wasn't enough clearance.
After a rigorous background check, the consultant finally received high-level security clearance to access the sensitive government archives.
From clear + -ance.
Uncountable when referring to the physical space between objects; countable when referring to specific official permissions or types of stock sales.