Related Clues:

• Certain barrier to entry
• A drawbridge may span it
• Defense that may be all wet
• Confine behind bars
• 'La __ aux Folles'
• "La __ aux Folles"
• Watery fortification
• Detains The Animals touring Cambridge
• Safety feature for zoo visitors
• Gerbil holder
• Home to a zoo crocodile, perhaps
• About time to shut up
• Silver taken in church — just a pound!
• Onetime Tower of London surrounder
• Barrier to entry?