Possible Clues:

• Phrase on a treasure map
• That's where it is!
• Unknown treasure guide?
• Treasure map hint
• Treasure map phrase, or a hint to making sense of the starred clues' answers
• Hint that you must use several times to find the hidden gem in this puzzle's grid
• Treasure map phrase
• Treasure hunt phrase ... or a hint to seven Across answers
• Treasure-indicating phrase, and a hint to the first words of the starred answers
• It's the very place ten MPs take short breaks