Final answer:
Seeing a red flashing light from the control tower while backtracking on the active runway indicates that a pilot should immediately taxi clear of the runway to avoid safety hazards.
Step-by-step explanation:
If you are backtracking on the active runway at an aerodrome for takeoff and you see a red flashing light from the tower, it means you should taxi clear of the runway. This is a signal indicating that the runway is unsafe, and you are to clear it immediately to avoid potential collisions or other safety hazards. It is crucial in aviation to understand and promptly respond to light signals from the control tower for the safety of all aircraft and ground personnel.