The upshot of an action is the end result, whatever happens last as a consequence of the original action. The upshot of reading this sentence is that you will understand what the word upshot means.
In the 16th century, the last arrow launched in an archery competition was called the upshot. Like that final arrow, the upshot is the conclusion, the outcome. Sure, you can eat ice cream really fast, but the upshot is that you’ll have a brain freeze. The upshot of eating ice cream slowly is that it will melt. Decisions, decisions.