Not long after you arrive at Chapter 4: The Slums, you will be greeted by a robot known as The Guardian. After a brief interaction with them and a cutscene showing all of the other robots emerging from their hiding place, you will be able to explore this area to your heart's content.
Stray basketball mayhem!
To the right of The Guardian is a set of steps that lead down to a merchant and two other robots who are rummaging through garbage. At the top of these stairs is a basketball conveniently placed in front of a slope that leads to a garbage can.
All you need to do is gently push the basketball so that it goes into the garbage can and you will net yourself this lovely little bronze trophy. If you miss, go off and explore The Slums for a little bit and the basketball will reset, allowing you another go to earn this trophy.