add_filter('woocommerce_checkout_fields','new_input_field_classic_checkout_clear_fix');

function new_input_field_classic_checkout_clear_fix($fields) {
    $fields['billing']['additional_info'] = array(
        'type' => 'text',
        'label' => 'Additional info',
        'priority' => 121,
        'required' => false,
        'clear' => true,
    );
return $fields;
}