Possible Clues:

• Slab on a grave
• Chief's approach that shows where one is lying
• It carries grave information for Dickens character
• Its stands over a grave, duly inscribed
• Memorial of one's death
• You're late if you've got this over you
• Principal's manner of speaking betokens a grave situation
• Death's one sad memento mori
• Memorial to leader's character
• Memorial for Dickens's would-be homicidal schoolmaster