What does the requirement that a planet must have "cleared the neighborhood" entail?

Answer

Through gravitational dominance, it has accreted or ejected most other small objects in its orbital path

Clearing the neighborhood means the body is gravitationally dominant in its orbital zone, having either incorporated or flung away the majority of other small celestial debris that shares its path.

What does the requirement that a planet must have "cleared the neighborhood" entail?

#Videos

What is a Planet? - Science at NASA - YouTube

DefinitionSpaceNASAastronomyplanet