Meaning of CLEARANCE in English

clear ‧ ance /ˈklɪərəns $ ˈklɪr-/ BrE AmE noun

[ Word Family: noun : ↑ clarity , ↑ clearance , ↑ clearing , ↑ clarification , ↑ clearness ; verb : ↑ clear , ↑ clarify ; adverb : ↑ clear , ↑ clearly ; adjective : ↑ clear ≠ ↑ unclear ]

1 . [uncountable and countable] the process of getting official permission or approval for something:

She’ll race if she gets medical clearance from her doctor.

Morris did not have a security clearance.

2 . [uncountable and countable] official permission for a plane to take off or land

clearance for

The pilot requested clearance for an emergency landing.

3 . [uncountable and countable] the removal of unwanted things from a place:

the clearance of minefields

snow/land/slum etc clearance

flooding caused by forest clearance

4 . [uncountable and countable] the amount of space around one object that is needed for it to avoid touching another object:

There was less than a foot’s clearance between the ship’s sides and the wharf.

5 . [uncountable and countable] a process by which a cheque goes from one bank to another

6 . [countable] an occasion when a player in a game such as football kicks the ball away from his or her ↑ goal

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.