Related Clues:

• It's no no-brainer
• Appropriately named monthly of the National Puzzlers' League, with 'The'
• Perplexing problem
• WWII encryption machine
• Closed book
• Wannabe
• Something of a mystery
• Insincere sort
• Head-scratching question
• Math question
• One pretending to like trendy music, say
• Tricky puzzle
• "Something wrong?"
• Spore raises a difficult question
• Puzzling question for the model