More appropriately, there's no standard way to do this with CL. One might ask the same about threads. What are threads? We just don't know.
Threads are not "standard" but the last thread-less Common Lisp just got them this month. Every maintained Common Lisp implementation today has Threads; and all support Bordeaux-Threads.
Show me a single mainstream language where threads are "standardized" other than Java?
My awkward phrasing was a reference to about 1:53 in this: http://www.youtube.com/watch?v=bCWA7uevo_Q