Aftab, Random number generators are really pseudorandom (deterministic). This means for a given "seed" you can consistently regenerate the same sequence. This is useful if you want to re-run your experiment or perform multiple experiments on the same random stream.
In short, yes, using clock to reset the seed with generate a different stream each time since the clock is different each moment. However the recommended way to change the seed is to use the RNG function:
Also all the link provided by SS and Ben are relevant.