GeoDirectory categories are normal WordPress taxonomy terms. Each post type has its own category taxonomy, named after the post type with category on the end: Places use gd_placecategory, and a post type called gd_event uses gd_eventcategory. That means a standard tax_query works and you don’t need a custom join.

To find a category ID, go to Places > Categories, hover over the category and look for tag_ID= in the edit link.

With WP_Query

$query = new WP_Query( array(
	'post_type'      => 'gd_place',
	'post_status'    => 'publish',
	'posts_per_page' => 20, // -1 for all
	'tax_query'      => array(
		array(
			'taxonomy'         => 'gd_placecategory',
			'field'            => 'term_id',
			'terms'            => array( 85 ),
			'include_children' => true,
		),
	),
) );

if ( $query->have_posts() ) {
	while ( $query->have_posts() ) {
		$query->the_post();
		echo '<a href="' . esc_url( get_permalink() ) . '">' . esc_html( get_the_title() ) . '</a><br>';
	}
	wp_reset_postdata();
}

To read a GeoDirectory field inside the loop, use geodir_get_post_meta( get_the_ID(), 'phone', true ), where the second argument is the field key.

With geodir_get_widget_listings()

This is the function behind GD > Listings. It reads from the GeoDirectory listing table, so every result already has the custom field values, and it accepts GeoDirectory sort values such as az and latest.

$listings = geodir_get_widget_listings( array(
	'post_type'      => 'gd_place',
	'posts_per_page' => 20,
	'order_by'       => 'az',
	'tax_query'      => array(
		array(
			'taxonomy' => 'gd_placecategory',
			'field'    => 'id',
			'terms'    => array( 85 ),
		),
	),
) );

foreach ( $listings as $listing ) {
	echo esc_html( $listing->post_title ) . '<br>';
}

With the REST API

https://example.com/wp-json/geodir/v2/places/?gd_placecategory=85

Here places is the post type’s slug. See Endpoints and Filter search results from the GeoDirectory REST API.

Without code

To display the listings rather than process them, the GD > Listings widget has a Categories filter: [gd_listings post_type="gd_place" category="85"].