Possible Clues:

• Marquis de - - , French soldier and writer 1740-1814
• Band with the debut album "Diamond Life"
• "Diamond Life" band
• Unhappy Eastern marquis as novelist
• Wooden barrier
• "Marat/___" (1963 Peter Weiss play)
• One-named Grammy winner for 'Soldier of Love'
• Grammy-winning singer with the 2010 album 'Soldier of Love'
• One-named British-Nigerian singer
• 'Your Love Is King' singer