Possible Clues:

• '...like a big pizza pie, that's ___' (old song lyric)
• What that is, in a 1953 song
• It's "when the moon hits your eye like a big pizza pie"
• 91-Down, Italian-style
• Viola d'___
• Martin's 'That's ___'
• Love of Livorno
• Dino sang about it
• Subject for Enrico Caruso
• Strong emozione