add_filter('nectar_post_grid_excerpt','salient_child_custom_query_portfolio_excerpt');

function salient_child_custom_query_portfolio_excerpt($content) {
  global $post;
  $project_excerpt = get_post_meta($post->ID, '_nectar_project_excerpt', true);
  $excerpt_markup = (!empty($project_excerpt)) ? '<div class="nectar-post-grid-item__excerpt-wrap item-meta-extra"><span class="meta-excerpt">' . wp_kses_post($project_excerpt) . '</span></div>' : '';

  return !empty($excerpt_markup) ? $excerpt_markup : $content;
}