Possible Clues:

• Mark, perhaps, too disorderly
• Entr'acte part
• Mark's rhetorical digression
• Cat-o'-nine-tails feature
• The poor sap's work abused by tradespeople
• Certain punctuation mark
• An oft-mistaken sign of omission
• Feature of mason's mark
• Passage addressed to character in Charley's Aunt ?
• What you see with 'apple's'? It's upsetting to a shopper!