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The ground is there as a safety precaution, so that if:
a) the live (hot) touches a piece of metal that it isn't supposed to, like the case that here has been flayed away, or
b) the neutral (return) wire touches the case *and* the load in the circuit the clock is plugged into is unbalanced
then the current will go through the case, down the ground line (which is attached to the case) and into the earth.
Without the ground conductor attached, if either (a) or (b) happened and someone touched the clock's case while it was happening they'd get lifted by mains power.
FYI: Ground Fault Circuit Interrupt (GFCI) plugs (like the ones that are usually in bathrooms with the "Test" and "Reset" buttons in the middle) go an extra step by monitoring the connections and if current begins to leak (i.e. go from hot/neutral to ground, like in the above example) it isolates the device, i.e. disconnects it from the mains. You would then have to hit the reset button to get the plug working again, but the shock you get would be so small and quick that you probably wouldn't even feel it.
Clarify that.