The history displays actions you've applied to spyware and other potentially unwanted software that Windows Defender has detected on your computer. To clear the history manually, Please follow the below steps:
1. Open Windows Defender by clicking the Start button Picture of the Start button, clicking All Programs, and then clicking Windows Defender.
2. Click History.
3. To delete all items in the list, click Clear History. Administrator permission required If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
The Windows Defender scan results log files in the folders below are encrypted and cannot be viewed.
However, you can view Windows Defender "Operational" events in Event Viewer (eventvwr.msc) under Applications and Services Logs -> Microsoft -> Windows -> Windows Defender.
With WinUtilities PRO, you can clean the Windows Defender temporary files from your system easily and safely. Just one click, WinUtilities PRO will analyze your drives for Windows Defender temp files first, and then clean them safely.