Related Clues:

• Works up a sweat
• Breaks one's back, say
• Grinds
• Works like a dog
• Doesn't do the job easily
• Herculean efforts
• Works a double shift, e.g.
• Works very hard
• Toils away
• Works in the mine, say
• Feats for Hercules
• Plugs away
• Herculean dozen
• Hercules' dozen
• Does drudge work