get foot in the door
get a/(one's) foot in the door
To have a chance to do something that could lead to further opportunities. The phrase is often used to refer to employment. An internship might not sound very interesting, but it's a great way to get your foot in the door at this company.
get one's foot in the door
Fig. to complete the first step in a process. (Alludes to people selling things from door-to-door and blocking the door with a foot so it cannot be closed on them.) I think I could get the job if I could only get my foot in the door. It pays to get your foot in the door. Try to get an appointment with the boss.