Dominykas

/**
 * Get products from events category and sort by woodate.
 *
 * Alter the main loop
 *
 * @uses pre_get_posts hook
*/
function theme_modify_the_main_query( $query ) {
    // Order by: woodate
    if ( isset( $_GET['orderby'] ) && $_GET['orderby'] == 'woodate' ) {
        // Modify the main query
        if( ! is_admin() && $query->is_main_query() ) {

            // Get from Events category
            $tax_query = array(
                array(
                    'taxonomy' => 'product_cat',
                    'field' => 'slug',
                    'terms' => 'events' // Events category (term) slug
                )
            );

            $query->set( 'tax_query', $tax_query );

            $query->set( 'meta_key', 'woodate' );
            $query->set( 'orderby', 'meta_value_num' );
            $query->set( 'order', 'DESC' );
        }
    }
}
add_action( 'pre_get_posts', 'theme_modify_the_main_query' );