leg-up 
noun [in singular] British
1An act of helping someone to mount a horse or high object: give me a leg-up over the wall...
- When Rattigan found the window was open, Wyatt gave him a leg-up in order to get in, but remained outside himself.
1.1An act of helping someone or something to improve their situation: he gave hip-hop a much-needed leg-up...
- The government's good intentions about giving young people a financial leg-up on the ladder of adult life will fall far short of the amounts needed to meet major commitments, it has been claimed.
- A former jockey has developed this revolutionary lightweight racing saddle after being given a leg-up by European funding.
- With this mortgage we hope to give them the leg-up necessary to help them realise the dream of their first home.
Phrases
have (or get) a leg-up on