Possible Clues:

• A way to evade an obligation
• Way out of a contract
• Get-out
• Deficiency in lavatory rod restricting flush finally
• Means of escape from rising water covering unpleasant place
• Legal out
• Ambiguity allowing one party to escape contract
• Out
• Weakness in law that's useful for defence
• Ambiguity that makes it possible to evade an obligation