// Вкладка Краткое описание
function description_product_tab( $tabs ) {
   
    $custom_tab_s = array( 
       'custom_tab_s' =>  array( 
     'title' => __('Описание','woocommerce'), 
     'priority' => 10, 
     'callback' => 'description_product_tab_content' 
     )
     );
    return array_merge( $custom_tab_s, $tabs );
}


function description_product_tab_content() {
    echo '<h2>Описание</h2>'; 
    echo the_excerpt(); 
} 
add_filter( 'woocommerce_product_tabs', 'description_product_tab' );