Please check the following link which is a custom component for achieving the tool tip requirement .
It was created for 10g , you might need to tweak it somewhat for getting it to work with 11g .
If I'm reading the OP's request correctly, I *think* the requirement is to add a title attribute to each individual option contained in a SELECT list. While such an approach saves real estate on a page, it's a bit of a nuisance to have to hover over each individual option in a list to get this additional information, especially if the list is long. This reminds me of Jakob Nielson's longstanding comments on usability when he called such a navigation technique a "mystery meat" approach.
Srinath's suggestion to me is cleaner (and is actually doable in WebCenter Records without the need for the extra component - so how did the functionality make it into one branch of the product, but not the other???). If you must nave the functionality for each individual option in the list, you'll have to edit the include "std_resultset_option_list_item" to add a 'title' attribute (and address the logic to determine the actual tooltip value, depending on how the option list data itself is being generated).