Cache that damn thing.. http://programming-perils.com/155/parse-less-files-on-the-fly-and-serve-them-as-css/

gistfile1.aw

<?php
$css = $_GET['path'];
$less = str_replace(".css",".less",$css);
file_exists($less) and $compiled_css = str_replace(".css", filemtime($less) . ".css", $_GET['path']);

if (!empty($compiled_css) and !file_exists($compiled_css))
{
	header("Content-type: text/css");
	$less_command = "/var/www/node/node_modules/less/bin/lessc ".realpath($less)." ".realpath($compiled_css);
	shell_exec($less_command);
}

if (file_exists($compiled_css))
{
	header("Content-type: text/css");
	$css_file = file_get_contents($compiled_css);
	echo $css_file;
}
else
{
        # Just in case you haven't configured your error levels appropriately in you production env.
        ob_start();
        trigger_error("couldn't find/compile $less");
        ob_end_clean();

	header("HTTP/1.0 404 Not Found");
	echo "Not Found";
}

Not tested.. should work though