Kill someone, as in They threatened to stop his clock if he appeared on the witness stand. This expression transfers the ticking of a clock to the progress of one's life. [Slang; 1940s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.