Gleditsia triacanthos, commonly called honey locust, is my first guess. We are located in North America, so check locally to see which trees are in your area. Some trees have large root systems, sending suckers far from the original tree. A grove of trees will form if the root suckers are allowed to grow.
I suggest you dig this sprout, to see if it is connected to a large root system. If so, you can find information about dealing with a suckering tree.