in finance, the verification of information between the two brokers in a securities transaction

a security clearance

in engineering and safety, a physical distance or space tolerance, as in a truck (lorry), train or boat under a bridge as well as a train in a tunnel (see structure gauge and loading gauge).

a closeout or final sale

an authorization or permission from an authority, for example:

in aviation, from air traffic control for an aircraft to proceed with a takeoff or landing, or other action

in medicine, clearance is the rate at which a substance is removed or cleared from the body by the kidneys and/or in renal dialysis.