Related Clues:

• Investigator's question
• It should be airtight
• 'The dog ate my homework,' e.g.
• Saving yarn?
• Use one's noodle
• Youngster's perpetual question
• Out, of sorts?
• Whodunit plot element
• Coffee-filter filler
• Wherefore
• 'I was at home washing my dog,' e.g.
• Defense aid
• Cop-out
• Out of sorts?
• Incentive