How do I backup data for a single app?

[AC Question]

My fiancé has been having trouble with a game crashing *constantly*, Frozen Free Fall. Sometimes she gets the message "Unfortunately free fall has stopped" while playing, but most of the time it just crashes without saying anything. I want to "Clear cache" for it, and also "Clear Data", but she is on a really high level for the game and she doesn't want to lose her saved data. So, how could I save that data so that I could "Clear data" or even do an uninstall / reinstall and still get her saved game back? I do *not* want to backup her entire phone, just that game. Any suggestions on the data backup, or fixing the crashing, is appreciated. Thank you!