The definition isn't exactly "cleared its orbit", but rather "gravitationally dominates its orbit". Neptune fits these criteria, because while Pluto does cross its orbit it is locked in a resonant orbit with Neptune. Similarly, the Moon, as well as Cruithne and several other near-earth objects, are all locked in a resonant orbit with the Earth. However the asteroid belt is not resonant with Ceres.
what if the earth was not a moon of another planet but was in an orbital resonance with that larger planet. we'd still not be considered a planet. this planet definition seems pretty arbitrary to me. the astronomy world feels like it's self-defining something to justify pluto not being a planet.
Alternatively: Neptune is locked in a resonant orbit with Pluto. Likewise, and even more so for the Earth and Moon, and Pluto and Charon. It's not a quantitatively exact specification.
