Use the same function as for search and home page listings. It is called osc_item_description()... but I suggest customizing it as such...
oc-includes/osclass/helpers/hItems.php function osc_item_description_extract($locale = "") {
if ($locale == "") $locale = osc_current_user_locale() ;
$extract = trim(preg_replace('/\s+/', ' ', strip_tags(osc_item_field("s_description", $locale))));
if ( strlen($extract) > 175 )
$extract = substr($extract, 0, 172) . '...';
return $extract;
}
This will take the item's description, remove all HTML, and strip all new line characters. You end up with a blob of text about 175 characters in length. Now you just need to drop it into the meta description tag.
oc-content/themes/modern/item.phpBetween the <head></head> section, add...
<!-- Search Engines -->
<meta name="description" content="<?php echo preg_replace('/"/', '', osc_item_description() ); ?>" />
See:
http://bit.ly/es1pUw (right-click > view-source)