Removing Queue Table Items / Queue UI Module D7
The default Drupal supplied queues only exist when they have $items within them. It will be regenerated when it's next inserted into.

Depending on whether or not a worker process is working on a claimed item the queue item(s) when you delete the queue -- you may raise like a warning when the process tries to notify the queue of completion of an item. It shouldn't break the queue itself; the worker processes may need to be reset of course.