Answer: knuckledown

AnswerCrossword Clue
KNUCKLEDOWNGet serious
KNUCKLEDOWNApply oneself earnestly
KNUCKLEDOWNGet to work
KNUCKLEDOWNApply oneself to a task
KNUCKLEDOWNGet serious about working
KNUCKLEDOWNApply oneself vigorously
KNUCKLEDOWNFloor scrubber's condition?
KNUCKLEDOWNGet serious at work or school