Related Clues:

• Nullify or disprove
• Nullify, disprove
• Render null or disprove
• Disprove or nullify
• Turn over and don't get down to one of 30 across
• DNE?
• Will this invalidate the northeastern entrance?
• The way to turn DNE over?
• The turnover you get from DNE?
• Does this cancel out the way in at the end?
• The turnover you get if it's not down at last
• This will cancel out the barrier at last
• Invalid ate this?
• Are you soft at last to get a turnover?
• This will make nothing of what you've got to open at last