add_action( 'woocommerce_after_shop_loop_item_title', 'custom_field_display_below_title', 2 );
function custom_field_display_below_title(){
    global $product;

    // Get the custom field value
    $custom_field = the_field( 'start_date' ); 
 
    // Display
    if( ! empty($custom_field) ){
        echo '<p class="my-custom-field">'.$custom_field.'</p>';
    }
}