You can configure the Space settings to hide the space portal content, which is Announcement, Threads, Apps, People, and Related apps & spaces.

• The space portal content that can be hidden

Click the Options icon at the upper right of the screen, and click Space settings. Note that the Space settings option is only displayed for space administrators.

In the Contents in space portal page section on the Space settings dialog, uncheck the checkbox for the content you want to hide.
The Contents in space portal page section can be configured only when Enable multiple threads is enabled.
Reference: Changing space settings