thing,
There is no "glide clear" rule. Here are the rules:
91.119 Minimum safe altitudes; general
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere – An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas – Over any congested area of a city, town, or settlement, or over any open-air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.