You'll have to think hard, there's no way to "clear" it. If there were, it wouldn't be of much use, would it? Someone steals your phone, resets the password, uses it instead of the fingerprint and they're in. If you've been keeping your phone backed up (you should be - always), just factory reset it (you'll still have to remember your Google login and password - there's no way around that), restore the backup and do the fingerprint thing again.