old hand at something
an old hand
One who has experience doing a particular task. If you have any questions, ask Andrea—she's done this job before and is an old hand at filing. I've been a bus driver for seven years, so I'm an old hand at this.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
old hand (at something)
n. someone experienced at doing something. I’m an old hand at fixing cars.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.