How to remove an order field ?

Howdy!

You can use the following code:

add_filter( 'woocommerce_checkout_fields' , 'custom_remove_woo_checkout_fields' );
 
function custom_remove_woo_checkout_fields( $fields ) {
unset($fields['billing']['billing_address_2']);
unset($fields['shipping']['shipping_address_2']);
return $fields;
}

Further information can be found here:

https://docs.woocommerce.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/

This custom code should be added to your child theme’s functions.php file or via a plugin that allows custom functions to be added, such as Code Snippets. Please don’t add custom code directly to your parent theme’s functions.php file as this will be wiped entirely when you update.

Cheers!