To delete your Grok chat history on grok.com/app and X, go to the chat settings...

https://technivorz.com/what-pages-do-i-need-to-visit-to-delete-everything-tied-to-grok/

To delete your Grok chat history on grok.com/app and X, go to the chat settings and select “Delete History.” Remember, deleting chats won’t remove any files or Imagine media—they need to be deleted separately from their folders