Using CSS you cannot, CSS will only change the appearance of the span. However you can do it without changing the structure of the div by adding an onclick handler to the span:
<html>
<head>
</head>
<body>
<div>
<a href="http://www.google.com">
<span>title<br></span>
<span onclick='return false;'>description<br></span>
<span>some url</span>
</a>
</div>
</body>
</html>
You can then style it so that it looks un-clickable too:
<html>
<head>
<style type='text/css'>
a span.unclickable { text-decoration: none; }
a span.unclickable:hover { cursor: default; }
</style>
</head>
<body>
<div>
<a href="http://www.google.com">
<span>title<br></span>
<span class='unclickable' onclick='return false;'>description<br></span>
<span>some url</span>
</a>
</div>
</body>
</html>