Go to this Amazon site to delete, edit or view all your notes and highlights:
https://kindle.amazon.com/your_reading
If you do it at that site, your records at Amazon AND on the Kindle WiFi will be adjusted. In addition at that site you can do mass deletions at one time or selective deletions.
Editing the Clipping file on the Kindle WiFi does NOT change your records with Amazon or in the eBooks.