Possible Clues:

• Bound to be the first of four sea sons
• Bound to get around at last to make the clock work
• Leap year, partly
• 'Bound then to be a son of the sea, perhaps (6)'
• It follows 35-Down
• Mattress part
• If winter comes, can ... be far behind? (Shelley)
• Make a confession about advertising some time before the summer
• Pogo-stick part
• Free water