It does...
float frameTime = frameClock.GetElapsedTime();
frameClock.Restart();
return frameTime;
... that's why it was removed.
No not a direct function, but the equivalent what Laurent has posted... ::)
// Outside the game loop
sf::Clock frameClock;
// Inside the game loop
sf::Time frameTime = frameClock.restart();
float seconds = frameTime.asSeconds();
// Obviously this could also get done directly without a sf::Time object.
Then again if you need it for physics you should think about a fixed time step. ;)