Final answer:
An airside area is a secured part of an airport that requires ATC clearance to enter, ensuring safety and authorized access.
Step-by-step explanation:
An airside area refers to the part of an airport that is accessible to aircraft, including runways, taxiways, and apron or ramp areas. To enter this area, one must obtain clearance from Air Traffic Control (ATC). This is essential for ensuring safety and security, as airside areas are highly controlled environments where aircraft operate. Clearance ensures that only authorized personnel and vehicles are present, reducing the risk of accidents or intentional harm. Typically, clearance would involve communicating with ATC using radio or through pre-arranged signals, to ensure coordination and control over the movement in these areas.