Possible Clues:

• Legal license
• Allow, authorise
• Straight hair may allow one todo this to it
• Allow - visa
• What can you do with straight hair? Pass
• You have to have permission to do this with straight hair
• Does this allow one to have a wave with it?
• This gives one leave to deal with the straight hair
• Allow a comment from the hairdresser?
• Let; enabling document