To keep your clients from risky places or to restrict access to specific pages from the clients, you can customize your WordPress dashboard by adding the below code in your theme's functions.php. This code allows you to hide parts of the WordPress dashboard menu.

function dcg_customise_dashboard() {
    // remove_menu_page( 'index.php' );                  //Dashboard
    // remove_menu_page( 'jetpack' );                    //Jetpack* 
    // remove_menu_page( 'edit.php' );                   //Posts
    // remove_menu_page( 'upload.php' );                 //Media
    // remove_menu_page( 'edit.php?post_type=page' );    //Pages
    // remove_menu_page( 'edit-comments.php' );          //Comments
    // remove_menu_page( 'themes.php' );                 //Appearance
    // remove_menu_page( 'plugins.php' );                //Plugins
    // remove_menu_page( 'users.php' );                  //Users
    // remove_menu_page( 'tools.php' );                  //Tools
    // remove_menu_page( 'options-general.php' );        //Settings
}
add_action( 'admin_menu', 'dcg_customise_dashboard' );

You need to uncomment the line ( remove // ) for the page that you want to hide/remove from the WordPress menu.

Be aware that this only hides the menu items from the dashboard and clients can still theoretically access these menus with a direct link (if they know).