Real Dictionary

crack the whip in British English
to assert one's authority, esp to put people under pressure to work harder
to make people work very hard and treat them strictly and perhaps harshly
noun: a game in which players in a line, each holding the next, run, roller-skate, or ice-skate for a distance until the leader veers suddenly in a new direction, causing the rest of the line to swing around rapidly and the players at the end of the line to los
verb: to demand obedience, hard work, or efficiency from others in a harsh or stern manner