it will clear the data. you will probably need to restart your phone after though. but no, it will not harm anything clearing that data, it's only temp storage, no longer used after whatever it was for was installed
edit: actually, I would restart your phone, let it idle for like 5 minutes just to be sure everything is loaded, then go in there and clear that data, then exit out using the back button, then restart the phone again and let it idle again for like 5 mins to make sure everything is loaded before using anything