请尝试以下代码：

$pro_args = [];
$pro_args[\'post_type\'] = \'post\';  //Replace your post type
$pro_args[\'post_status\'] = \'publish\';
$pro_args[\'posts_per_page\'] = -1;
$pro_args[\'tax_query\'] = array(
    array(
      \'taxonomy\' => \'category\', //Replace your taxonomy name
      \'field\' => \'id\',
      \'terms\' => array( 66 ),
    )
);

// Optional
$pro_args[\'meta_query\'] = array(
    \'relation\' => \'AND\',
    array(
        \'key\'     => \'key1\',
        \'compare\' => \'EXISTS\',
    )
);

$pro_query  = new WP_Query( $pro_args );

if ( $pro_query->have_posts() ) {

    while ( $pro_query->have_posts() ) { $pro_query->the_post();

        delete_post_meta( get_the_ID(), \'key1\' );

    }

}

wp_reset_postdata();