You can delete a run in the Resume game menu by long-pressing on a game. This only works if you have at least two in-progress games.
If your game has at least 30 minutes of playtime, then this let's you submit the game for a score.
What FuzzyEuk says. Also, when you do so, the game will be simulated to the end, so you might get xp for a few more rounds, depending on your defense :-)