Possible Clues:

• "S" on an invitation, maybe
• "The Sopranos" second in command, for short
• Part of a certain ''response''
• French contraction
• Tony's consigliere on 'The Sopranos'
• The S in RSVP
• The 'S' in 54-Down
• Steven Van Zandt's role on 'The Sopranos,' informally
• — vous plaît
• Comstock Lode excavation