CLEARANCE

noun Date: 1540 an act or process of clearing: as, the removal of buildings from an area (as a city slum), the act of clearing a ship at the customhouse, the offsetting of checks and other claims among banks through a clearinghouse, certification as clear of objection ; authorization , a sale to clear out stock, authorization for an aircraft to proceed especially with a specified action , the distance by which one object clears another or the clear space between them, the volume of blood or plasma that can be freed of a specified constituent in a specified time by its excretion into the urine through the kidneys