Is it possible to cluster KML features in OpenLayers, and are there any samples?
I can find separate samples for clusters and KML but nothing which handles both together.
It's definitely possible. Add your KML file as layer type = Vector, protocol = HTTP, format = KML, and add a Fixed and a Cluster strategy to your list of strategies[]. Assuming you have code to work from since you mentioned you've seen examples of both. If not, look at samples here:
http://dev.openlayers.org/releases/OpenLayers-2.12/examples/