Related Clues:

• Brain teaser
• Puzzle; sieve
• Run through unsolved problem
• But Bowie fans rate it highly
• Puzzling person, thing
• Let the Ashes slip through this problem
• Get upset about theologian posing puzzle
• Eg, When is a door not a door?
• Make many openings in puzzle
• It may have an answer, but it's full of holes
• Problem to sort out
• Ingenious question
• Cryptic question
• Harry set about extremely dated puzzle
• Inspector finally departs having cracked trivial mystery