You can delete all the cards form the list and then delete the (empty) list.
If you in future would need the list again, or would need part of the list, then you can re-import it. That is no problem.
To delete the list using the application, swipe on the name of the list and you will get additional buttons to use (on Android instead of swiping keep your finger on the list name for about 2-3 seconds)