Possible Clues:

• Something mysterious or puzzling
• Game in crackers is a puzzle
• Mysterious thing
• 'In' game with which to monkey puzzle
• Variations in code who could possibly imagine? Not I
• Tough puzzle
• Puzzle cryptically written by one finishing below
• Imagine losing one when shaking riddle!
• The answer to this is to have a gin with me
• Altered image about me, finally, in this puzzle