Possible Clues:

• Bowel movement doctor agrees is hard work
• Effort, so to speak
• Hard physical work
• It may be needed to get out a tough stain
• Ale brew goes swimmingly, but it's hard work
• Vigorous physical effort
• Hard rubbing (colloq.)
• Vigorous physical labour involving hard rubbing
• Extra effort, so to speak
• Hard work moving slow barge in middle of week