You can’t simply right-click the Defender icon and close it, nor can you open the Windows Defender interface and find an option to hide or unhide the icon.
Instead, the tray icon is produced by another program that launches when you sign into your PC. You can disable this autostart program form the Task Manager. To access it, right-click your taskbar and select “Start Task Manager” or press Ctrl+Alt+Esc on your keyboard.
Click the “More Details” button, then click the Startup tab. Locate the “Windows Defender notification icon” option in the list, right-click it, and select “Disable”.
This will disable the Windows Defender tray icon, and it won’t automatically start whenever you log in. You can sign out and then sign back in–or restart your computer–and the icon will be gone, though Windows Defender will still run.
To get rid of the tray icon without signing out of your Windows user account, you can close the process manually. Click over to the “Processes” tab in the Task Manager and find the “Windows Defender notification icon” process in the list. Right-click it and select “End Task”. The Windows Defender tray icon will immediately vanish.