It was removed because it was not as good as a user-side clock.
It was mainly used to get the elapsed time to pass to update functions, but:
- the returned time was wrong (last frame duration instead of time elapsed since last update)
- there's no reason for such a function to be in the sf::Window class
The new way of measuring the update time is 100% accurate (also thanks to the new sf::Clock::Restart function):
The other use of this function was to compute FPS, but I don't consider that it deserves a dedicated function in the public API.