productos por tienda

// WP_Query arguments
$args = array(
	'post_type'              => array( 'producto' ),
	'post_status'            => array( 'publish' ),
	'paged'                  => '$paged',
	'tax_query'              => array(
		'relation' => 'AND',
		array(
			'taxonomy'         => 'categoria',
			'terms'            => '$cat_id',
			'field'            => 'term_id',
			'operator'         => 'IN',
		),
	),
	'meta_query'             => array(
		'relation' => 'AND',
		array(
			'key'     => 'tienda',
			'value'   => 'online',
			'compare' => 'IN',
		),
	),
);

// The Query
$query = new WP_Query( $args );