function exclude_subcategory_posts_from_main_category($query) {
    if ($query->is_main_query() && !is_admin() && is_category('police-boot-offers')) {
        $query->set('tax_query', array(
            array(
                'taxonomy' => 'category',
                'field'    => 'slug',
                'terms'    => array('guides'), // Exclude the "Guides" subcategory
                'operator' => 'NOT IN'
            ),
        ));
    }
}
add_action('pre_get_posts', 'exclude_subcategory_posts_from_main_category');