The term "to shed a wing" means the wing or wings break away from the aircraft fuselage - the most common cause or reason for wing-shedding is the pilot exceeding the designed maximum airspeed for the aircraft

Generally caused by inexperienced pilots (and experienced VFR pilots who are non-IFR rated) who inadvertently enter cloud for whatever reason and, deprived of their "visual reference", end up with "spatial disorientation" which invariably creates what is called a "graveyard spiral" - the aircraft is turning and descending with increasing airspeed that the pilot is unable to control

Within a short space of time, generally less than two minutes, the aircraft has exceeded it's design airspeed and sheds a wing or two or impacts the ground