There isn't a clear way to delete your LiSTNR cache on iOS devices. An option that may help is to use the built-in Offload App option. This frees up storage space the app uses while still keeping its documents and data intact.
When you reinstall the app using the offload option, your data will be recovered. You'll need the latest version of the LiSTNR for this option to appear.
- Open the Settings app
- Tap General
- Select iPhone Storage
- Wait for the list of all your apps to load. Once the list appears, find the LiSTNR app and swipe it to the left
- Tap Offload App