Engine wont start?

I have a husqvarna yth1542xp, it won't start. It will give a clicking sound when I press the clutch/brake pedal however it will not turn the engine over. y battery power when checked using a volt meter indicates that it has 12.5 volts not connected to the electrical system. Do I need another starter? Quite often I have to muniplate the clutch pedal several times up/down to get the engine to run. Thanks