Why the filter is already applied


I need to clear this filter whenever i open Employee

That for, you have to applied the listview client script.

frappe.listview_settings['Employee'] = {
    onload: function(listview) {
        $(document).ready(function() {
            $('.filter-x-button').click();
        });
    }
};

oh in some of the documents it is like this so ineed to change in all

Reference:

Something like this scenario will happen.
This reference for doctype script, not for the listview.