Trouble was a bad situation where it usually meant that an individual had done something bad and would be punished because of it.
In 2365, Q referred to Guinan as an imp, warning Jean-Luc Picard, "This creature is not what she appears to be. She's an imp, and where she goes, trouble always follows." (TNG: "Q Who")
In 2372, when Brunt hired a couple of Nausicaans to assault Quark, Odo declared the assault to be an open and shut case. Despite that, Quark did not plan to press criminal charges, as he was already in enough trouble with the Ferengi Commerce Authority. (DS9: "Bar Association")