pick up what (one) is putting down
slang To understand what someone is saying, especially when something is insinuated, rather than stated directly. A: "I'm going to say that I'm busy on Sunday, and I think you should too." B: "I'm picking up what you're putting down—I don't want to go to this family reunion either!" If I see you around here again, there's going to be trouble. Are you picking up what I'm putting down?