In control of, fully informed about, as in The weeds were terrible, but the new gardener was soon on top of them, or Our senator always manages to be on top of the issues.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use on top of in a sentence
She remembered her old boss as being “one of those organized, on-top-of-it people” and “a straight arrow.”
But Natchez-on-top-of-the-hill is attractive; has always been attractive.Life On The Mississippi, Complete | Mark Twain (Samuel Clemens)