Possible Clues:

• 'Just a scratch, really' ... and a hint to the starts of 17-, 27-, 36- and 46-Across
• "Just a scratch, really" ... and a hint to the starts of 17-, 27-, 36- and 46-Across
• Polite response to a thank-you, or a comment about the start of 17-, 23-, 39- or 51-Across?