Answer: toiled

AnswerCrossword Clue
TOILED

Broke one's back

TOILED

Slaved away

TOILED

Worked arduously

TOILED
Worked
TOILED
Worked one's fingers to the bone
TOILEDPlugged away
TOILEDKept one's nose to the grindstone
TOILEDWorked really hard
TOILEDWorked hard
TOILEDWorked like a Trojan.
TOILEDLabored
TOILEDDug ditches, e.g.
TOILEDSlaved
TOILEDWorked like a dog
TOILEDWorked really, really hard
TOILEDWorked a 12-hour shift, e.g.
TOILEDApplied elbow grease
TOILEDSlogged away
TOILEDPut one's nose to the grindstone
TOILEDPut in work