Flinders Street Station is the Central Railway Station of Melbourne located right beside Federation Square.
This is the place where you can see a crowd of people on the streets. Unlike the usually empty streets of Melbourne. This is one of the Few places in Melbourne where the signal leads to a pedestrian scramble.
If someone tells you in Melbourne "I'll meet you under the clocks" then it simply means under the clocks in the station displaying the time for the next trains bound for different places. "I'll meet you on the steps" means the fleet of stairs leading to the station. You can usually find a quite interesting and diverse crowd there. Its probably the best place to experience the diversity of Melbourne.