What it means
A smokescreen is a distraction thrown up to hide what's really happening. Could be PR waffle, a side argument, or some big shiny drama meant to keep everyone staring at the fog while the real move happens off to the side.
Usage examples
"The grand announcement was just a smokescreen, three days later they quietly pushed through the unpopular cuts."
"The chairman’s press release about the green credentials of the company turned out to be a smokescreen for the closure of the Birmingham factory, three hundred employees on the way to redundancy and the carbon-offset announcement quietly dropped from the corporate website two days later."
"The minister threw up a smokescreen of statistics about the new transport budget during the Tuesday questions session in the Commons, and the journalists from the regional press who had travelled from Cumbria came out of the briefing as confused as before they had entered the chamber."
"That whole apology video was a smokescreen so nobody would clock the layoffs dropping on Friday."
"Don't get hypnotised by the budget speech, mate, half of it's just smokescreen while they sneak the dodgy bit through."
Where it comes from
Smokescreen started out as the literal military thing, a cloud of smoke used to hide ships, troops, or movement from the enemy. By the early 1900s it had drifted into everyday English, especially politics and journalism, where it came to mean any distraction or cover story used to hide what’s really going on.