Possible Clues:

• Ring again if you wish to reverse the charge
• Provoke disgust about act, initially � thus annul it
• Perhaps ring again if you want to annul this
• Annulment? Then you may get another ring!
• Significant outside pressure before East's revoke
• Cancel article in disgust
• Undo a law
• 'Annul, revoke (6)'
• Strenuous part of schooling in genuine reverse
• What to do to end the act?