To do away with a criminal cell, crew, or unit. Used by those in upper ranks when a crew has make unforgivable errors, and is an absolute last resort. Clearing the Books is done to prevent repercussions, and to save face to the higher ups. To make it as if an action never happened, erasing all parties involved in order to make room for someone more competent
The job that Trini's crew was on went to hell, he had only one shot to get it right. We're gonna have to clear the books on this one.