Windows Defender will not work with Spybot, or any other antivirus program I have tested so far, on Windows 10.
It seems that WD is only available on Windows 10 as backup security if no other security is installed.
From Microsoft:
When you install some 3rd party antivirus (AV) programs, they may automatically turn off Windows Defender. In this case you will not be able to turn on Windows Defender again until the 3rd party AV program has been completely uninstalled.
found here:
http://www.tenforums.com/tutorials/5...dows-10-a.html