How to add a solid background to an image thats transparent

[jford11609]

I have an image of a clock and the background of the clock is transparent. Im wanting to add a solid background to it without making the whole canvas that solid color (around the clock). Its a pretty intricate clock with lots of little spaces so it would take me forever to fill it with the bucket. I know there has to be an easier way to do this. Please help! I posted a link to something similar im working with. 
https://www.google.com/search?q=pocket+w...bTf1WBPuM: