Finish something or succeed before time is up, as in The paper went to press at five o'clock, and they hurried to beat the clock. The term comes from various sports or races in which contestants compete within a certain time limit.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.