Possible Clues:

• Platypus feature
• Aussie native is to evade payment
• Try to avoid payment for amphibian
• "Quack" comes out of it (2 words)
• ''Quack'' comes out of it (2 words)
• It's the Beak! Get your head down, Bill
• Monotreme with nothing on account
• Avoid President Clinton?
• Get your head down, William, down under
• Keep your head down, boy: Down Under that's not a bird's beak