Wiktionary
get a leg up
vb. 1 (context idiomatic English) To get a boost or a lift. 2 (context idiomatic English) To gain some advantage; to get a head start.
Usage examples of "get a leg up".
In what was obviously a well-rehearsed drill, Flora and Fauna laced their fingers together into a stirrup, so Diamond could get a leg up and climb onto the counter top.
Salary men and cor-porates were on their way home, or perhaps still clacking keyboards and tapping in orders in an effort to impress their bosses and get a leg up over their fellows.
If I called the jobbers in Boston with a rush order, I could get a leg up on the competition at the big Dartmouth Bookstore down the street.