Remove from a div by class name from post page if post author role is not administrator

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Basically you are asking a function to check the post author role. You can use user_can() function.

if(user_can('administrator'))
{
     //Write your code if the admin
}

current_user_can() : https://codex.wordpress.org/Function_Reference/current_user_can

user_can() : https://codex.wordpress.org/Function_Reference/user_can