The idiom a leg up means (1) a boost or (2) a position of advantage.1 When you get a leg up on your competition, you’re at least temporarily ahead of them in some significant way. The phrase comes from foot racing, where getting a leg up at the start of the race gives an edge.
These writers demonstrate how a leg up is conventionally used:
And he might have a leg up on the rest of the contestants because of his shooting style. [ESPN]
The so-called credit bidding gives a leg up to existing debt holders, because they wouldn’t have to put up fresh money. [Wall Street Journal]
Spurs head coach Gregg Popovich believes Toronto’s athleticism gives them a leg up against his squad. [Toronto Sun]
While a leg up is usually treated as synonymous with advantage, some writers use it to mean a head start, which is in keeping with the idiom’s racing origins—for example:
So if you’re interested in getting a leg up on 2012′s Oscar race, you’d do well to note Sundance’s most recent successes. [New York Daily News]
She added that the program gives the students a leg up on college and sparks a bright future. [Bradenton Herald]