A clicking starter relay is usually caused by low power and that can be from a bad or weak batters or a poor cable connection or any connection in line even a bad ground. It can also indicate that the engine is seized but if you remove the belt cover and rotate the primary by hand that can be eliminated. It could also indicate the starter has a problem but start with checking all the connections first....and do make sure the battery is good...there have been an abnormal number of battery failures recently.