Possible Clues:

• This will make nothing of what you've got to open at last
• Age ten (anag.)
• One wicket? Nonetheless, disallow!
• Invalid ate this?
• Deny; nullify
• Cause to have no effect
• Nullify - deny the existence of
• This will cancel out the barrier at last
• Nullify, disprove
• Does this cancel out the way in at the end?