Clear a single url from cache Using Drupal's standard cache system, is there a way to clear the cache for a node or url without clearing the entire cache (which slows down the whole site)?
The module Cache actions provide very fine grained control over your cache clearing.

Unfortunately, whether it will solve your exact problem depends on how this particular url is built up. In case it doesn't do exactly what you want, it's codebase would still be an excellent start for building more exactly what you need.