This button helps you cleaning the cache of a post instead of clearing all the cache.
How to Hide
If you do not need this button, you can hide it easily via the screen options. Please follow the steps;
1. Click on the “Screen Options” button
2. Disable the “Cache” option
3. Click on the “Apply” button
How to Remove from Screen Options
If you wanna remove “Clear Cache Button” from “Screen Options”, you need to add the following line into wp-config.php file.