This can’t be done without modification of services widget. I prepared modified file for you, download it from here. After that replace original file inside theme foldet / widgets / fp-services.php with new one (but backup original file). You will now have field with description http://screencast.com/t/z4is3kd2LIw
Note that for this kind of modification it is best practice to use child theme since changes will be lost on next theme update. If you decide to use child theme search forum for unregister widget since you have to unregister old one and to register modified one. In this way you will preserve changes after theme updates.
Also note that this is not covered with theme support but since I made modifications you can easily see how you should modify other widgets.
I hope you will find this answer useful