Possible Clues:

• Sign of the zodiac
• January sign
• Sign of the Goat
• Sign of growth supporting island in the Bay of Naples
• Something hackneyed under the island sign
• Sign on holiday island: 'Firm requires sailors'
• Zodiac sign
• Zodiac goat
• Goat of note
• Seems that the 6 across from the island is one of the 15 across