Possible Clues:

• and 10 Across and 21 Down: Hit from Simon the reason for deferring to Charles in diary?
• Why empty coffin's lightweight?
• There isn't any one of us that has only a soul
• Diarist, an insignificant person
• "I Ain't Got ___" (Louis Armstrong hit)
• Lightweight criticism of wine
• It's just spirit for no-one
• Eg Pooter's reason for not bringing murder charge?
• There isn't anyone that has what spirits have
• Diarist lacking in substance