I think Richiev's version is a definite improvement. Here is my revision of his version:
When a covert agent is branded a terrorist, he has 24 hours to stop the real terrorists from perpetrating the conspiracy he is accused of: triggering a nuclear war.
Ideally, a logline is about the sizzle -- not the steak. Is the sizzle that he's wanted for the murder of his wife? Is that what makes the story unique, different, gives it a twist? I don't think so. I think it's part of the meat -- the plot, an additional complication.
To me, the sizzle is that he's suspected of planning the very deed he's trying to prevent. That's what stands out,hooks my interest-- not the murder.
The murder is relevant to the objective goal (stop the conspiracy) IF and ONLY IF the murder is directly, causally linked to the conspiracy. Even then, it's a link he's will discover in the course of trying to stop the conspiracy. Solving his wife's murder would be nice, but it is not the primary goal. He has a more important, more pressing mission to worry about than clearing his name: he's got only 24 hours to save the world.
So I suggest that the logline focus on the primary objective goal, stopping the conspiracy, and save the murder reveal for the script.
fwiw.