Possible Clues:

• Nothing, nil
• Number in the Cookie Monster song "They Not Take That Away From Me"
• Sucky attendance count
• Lowest cipher
• This could give you 27 acrossin a seedy setting
• Number of calories in water
• Coldest temperature on the Kelvin scale
• Nought, nil
• N ought to do for this
• Thus nothing could make 33 down catch you