The message “Constant WP_USE_THEMES already defined in …/index.php” comes from the index.php file in the root of your WordPress install, not from GeoDirectory or your theme. That file sets the WP_USE_THEMES constant and loads WordPress. PHP complains when the constant is defined a second time, which means the file has been changed or something is loading it twice.

How to fix it

1. Back up your site files.
2. Open index.php in the WordPress root folder (the folder that holds wp-config.php). An unchanged copy is only a few lines long and looks like the example below.
3. If you see define( 'WP_USE_THEMES', true ); twice, or extra code above or below it, replace the file with the index.php from a fresh download of your WordPress version.
4. If the file looks normal, something else is loading it: a security, caching or maintenance plugin, or a custom setup on your host. Deactivate plugins one at a time until the notice goes, and ask your host if the file keeps changing.

<?php
/**
 * Front to the WordPress application.
 */
define( 'WP_USE_THEMES', true );

/** Loads the WordPress Environment and Template */
require __DIR__ . '/wp-blog-header.php';

An index.php that changes when nobody edited it can be a sign the site has been hacked. If that happens, run a malware scan and talk to your host.

Hide notices from visitors

Live sites shouldn’t print PHP notices on the page. In wp-config.php, either turn debugging off or keep logging but stop the display:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

This hides the message but doesn’t remove the cause, so still fix index.php.