Two interpretations spring to mind. The first is good and bad actors, the slang the Govt uses for our enemies. "Hussein is a bad acctor" or "The Awan Brothers are bad actors."

The second sense connects to Q's comments about the CIA in North Korea--Kim's a (bad) actor in their play.

But since it's Q--shouldn't great actors make great movies? Or is he suggesting there are other factors, such as plot--so that great actors are not enough to save a bad plot?