post_meta_query.php

<?php

// get all 'staff' post types with a '_hmc_staff_include_on' custom field value of 'executive_committee'
$staff = new WP_Query( array (
    'post_type' => 'staff',
    'posts_per_page' => 500,
    'meta_query' => array(
        array(
            'key'     => '_hmc_staff_include_on',
            'value'   => 'executive_committee',
        ),
    ),
) );

if ( $staff->have_posts() ) : while ( $staff->have_posts() ) : $staff->the_post();

        get_template_part( 'partials/content', 'staff-listing' );

endwhile; endif;

wp_reset_postdata();