Possible Clues:

• Good luck!
• Good luck playing Akela, bizarrely in production of 1984?
• 'Good luck!' ... and a hint to 17-, 25-, 39- and 51-Across
• Theatrical 'good luck!'
• Phrase used in the theatre to wish someone good luck
• Expression of luck
• Line delivered before lines are delivered
• Good luck in the theatre - but not on the piste
• Good luck wish offered to actor in bleak rage
• Ironic "Good luck!"