Possible Clues:

• Big spiral shell
• Type of shell
• Big spiral-shelled mollusc
• How one might get a blow in for Shelley?
• Triton's trumpet
• Spiral-shelled mollusk
• Sea-shell whose plural can be spelt with an unexpectedly missing 'e'
• One's sometimes pulled in to beach child's play -- I must be old
• Sea shell sometimes used as a wind instrument
• It's blown out of the water