Possible Clues:

• Oily liquid preservative — eco-store (anag)
• Black liquid, supplied by Native American, old drunk swallowed
• Greek island storing oil, primarily as preservative
• Oily liquid ruining eco-store
• Legendary bull's home pumped with oxygen thus, as preservative
• Island holds nothing so useful for preservation
• Dark liquid drunk by Osage leader, native American bottles
• Oil broken-down scooter with last of lube
• Chimney cleaner's target
• 'Double O' assumed by wily secret agent stopping the rot