Hi Bookworm
ICAO Annex 2
Air traffic control clearance. Authorization for an aircraft to
proceed under conditions specified by an air traffic control
unit.
Note 1.— For convenience, the term “air traffic control
clearance” is frequently abbreviated to “clearance” when used
in appropriate contexts.
Note 2.— The abbreviated term “clearance” may be prefixed
by the words “taxi”, “take-off”, “departure”, “en route”,
“approach” or “landing” to indicate the particular portion of
flight to which the air traffic control clearance relates.
and EU IR 923/2012 (SERA), Art 2
28. ‘air traffic control clearance’ means authorisation for an aircraft to proceed under conditions specified by an air traffic control unit;
2 s