The Rambam and Rabbeinu Yona define avak lashon hara as a statement which hints to or will cause lashon hara to be spoken. It’s very possible in most occasions one will also transgress lifnei iver, placing a stumbling block in front if the blind. Just as hitting an older child or loaning money without witnesses sets up a situation of sin, the parent is enticing his teenage or older child to hit him back, or the loaner is enticing the borrower to deny the loan and not pay it back, so to when you praise someone in front of their enemy or you say I don’t want to talk about it inevitably lashon hara will come out and your statement was the cause.
Saying I don’t want to talk about the matter is avak lashon hara, still prohibited but not outright lashon hara even though we said in the first chapter, halacha 8 that hinting to lashon hara is fully forbidden but there it’s referring to expressing a complete statement of lashon hara without saying it out loud like by winking or the like but here you are not expressing any lashon hara, rather you are just hinting to something that could lead to lashon hara. It is definitely forbidden to tell someone who asks about someone else “I don’t want to tell you because that would be lashon hara.” The best thing to do is try to avoid speaking, switch subjects or just say I don’t know.
The last examples of avak lashon hara in this halacha is the prohibition of overly praising someone even if it is not in front if his enemy because it will inevitably lead to either the speaker saying lashon hara because he’ll slip in a line, like “but he’s not always perfect…” or people in the crowd will chime in something of the like, “that’s not always true…” etc. There are even times that even some praise is forbidden if it implies that according to his standard or level there expected more of him in that area or in other areas.