What it means
Upshot is the end result or the main takeaway once all the arguing, explaining, and messing about is out the way. You use it to land the point fast, usually in stuff like The upshot is..., when nobody needs the full soap opera again and you just want the bit that actually matters.
Usage examples
"Had a moan at the chippy about cold chips and a dodgy pint. Manager did the apologies. Upshot is we got a refund and free pud."
"Long meeting, lots of waffle, but the upshot is we're hiring two more people in spring."
"They argued about it for weeks, upshot being nothing changed and everyone's still annoyed."
"We spent an hour going round in circles about the holiday, but the upshot is we're skint and staying home."
"Asked three different people, got three different stories. Upshot is the gig's cancelled, so don't bother heading in."
Where it comes from
It goes back to archery. An upshot was the final shot in a contest, the one that could settle it. From there it drifted into wider English for the final result or conclusion, the bit left standing once all the noise, detours, and back-and-forth have finished kicking up dust.