Remove address street field placeholder in checkout form

Paste the following in the theme’s functions.php:

/* Remove address street field placeholder */
// Hook in
add_filter( 'woocommerce_default_address_fields' , 'custom_override_default_address_fields' );

// Our hooked in function - $address_fields is passed via the filter!
function custom_override_default_address_fields( $address_fields ) {
     $address_fields['address_1']['placeholder'] = '';

     return $address_fields;
}

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