Ranger. I am of the opinion that cleared to land means that the runway is free from obstructions and/or ( in general) traffic. Obstructions (frangible or otherwise) outside of the fence or penetrating the horizontal surfaces are the responsibility of the Aerodrome Operator. It is incumbent upon THEM to make sure that there are none OR that they are properly NOTAMN'd . The responsibility for accepting a clearance rests with the pilot.
However as my old Boss used to drill in to us "ATC are never blameless"