Possible Clues:

• Sign of month about to hit hard
• A signature as souvenir
• Make a sign or put a hag like this
• Handwriting of author, a GP, that's appalling
• What's handwritten diagram showing data for car?
• (Celebrity) signature
• "Turn Up the Radio" '80s band
• A celebrity might be asked for one
• Most of page author used for signature
• Signature diagram of vehicle?