You do not need any third party app to clean your iOS devices.
iTunes categorizes cached music, videos, and photos as Other instead of actual songs, videos, or photos. Cached files are created when you stream or view content like music, videos, and photos. When you stream music or video, that content is stored as cached files on your iOS device so you can quickly access it again.
Your iOS device automatically removes cached files and temporary files when your device needs more space.
- Go back to Settings and tap General > Reset > Erase All Content and Settings. If you turned on Find My iPhone, you might need to enter your Apple ID and password.
- If asked for your device passcode or Restrictions passcode, enter it. Then tap Erase [device].
What to do before you sell, give away, or trade in your iPhone, iPad, or ...
https://support.apple.com/en-us/HT201351