You can use $_GET variables in your cron, but you pass the variables in seperated by spaces, like this
php /home/mydomain/public_html/clear-dead-clicks.php remove=1 > /dev/null 2>&1
A good idea is to a complete dump of $SERVER, $REQUEST, get_defined_vars, and even phpinfo() and write it to a file or email it to yourself from the script, as then you can see exactly what's available to you.
Things like FILE can be used instead of $_SERVER['SCRIPT_NAME']