To "get your foot in the door" means that you have a good opportunity to begin something or to get something. Imagine that a door is closing but you want to be on the other side. If you use your foot to stop the door, you can go through it. The idea is that by "getting your foot in the door," you will have the opportunity to be on the other side. Some examples: An internship is a great foot in the door to a new career. I want to get a promotion so I told my boss for more responsibility at work. It might be difficult at first, but I am trying to get my foot in the door. I don't have any experience abroad, but my company offered to send me to China for a week. It is not much, but it gets my foot in the door of international business. Notice that many times this is used when talking about work or a career. The idiom can be used in other instances, but I believe you will hear it most in regards to work.

I wouldn’t say this is a common use of the idiomatic phrase “foot in the door” but I’d take this to mean that “it’s a a great opportunity” hope that helps!