Related Clues:

• Goes around seasonal railway to passage for the boats
• Nerdy leaving New Year's Day by barge route
• Main trade route
• The main course
• Ship's path
• Main passage
• Ship's 34-Down
• The Saint Lawrence______
• Channel links Home Counties to 'abroad'
• Inland route for use by seagoing ships
• Shipping channel
• Wet shipping route
• Finally, isotopes come apart in heavy water
• Channel for shipping
• Its traffic clears bridges