The flight instructor reported that while holding short to cross runway 21L in a skid-equipped helicopter, she was issued the clearance "cross 21L." She reported that she assumed that the clearance was for a direct route to her destination on the airport. After the helicopter began to hover taxi direct to the destination, she reported that the ground controller called her and stated "cross 21L at C4, D4 and follow company traffic." The flight instructor reported that to avoid a runway incursion, she "turned the helicopter into a tailwind and considering the high density altitude and strong winds the aircraft did not have enough power and it settled toward the ground, causing one bounce in the sod, the second bounce rolled the helicopter onto its left side." The flight instructor reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. The helicopter sustained substantial damage to the tail boom.