Simply using a:hover in pure CSS is not sufficient, as the link will return to its normal state when the mouse moves out or other areas are clicked.
To address this, you must handle the click event on the specific anchor element. For instance, assuming all anchors have the class "product" and the wine name is used as the ID of the div:
$("a.product").click(function(e)
{
e.preventDefault(); // Prevents default action for the link
$("a.product").removeClass("active"); // Removes "active" status from other products
var name = $(this).parent.attr("id");
$(this).addClass("active"); // Sets selected item as "active"
// Implement your AJAX logic here...
});
The corresponding HTML could be:
<div id="wineName1"><a class="product">...</a></div>
<div id="wineName2"><a class="product">...</a></div>
<div id="wineName3"><a class="product">...</a></div>
In your CSS, target the larger image like this:
#wineName1 {...}
#wineName1 active { /* Styles for larger image go here */ }
As a side note unrelated to your query, structuring your wines with an unordered list (ul) may be more semantically appropriate.