Related Clues:

• Slaved
• Strained
• Worked like a dog
• Labored
• Worked
• Plugged away
• Put one's nose to the grindstone
• Worked hard
• Toiled
• Worked a 12-hour shift, e.g.
• Slogged away
• Applied elbow grease
• Worked up a sweat
• Worked arduously
• Put one's back into it