The public should be 'clued in' to what's happening. [=should be told about what's happening]
He doesn't have a 'clue' when it comes to fixing cars. [=he knows nothing about fixing cars]
He's totally 'clued in on' [=he knows a lot about] the latest computer developments.
(..) power over it and we can cast it out. Yeah, sure, but we don't know its name. But, maybe we do. Huh? Why else would he give us that clue? He must think that we know it somehow. So, what do you do now? An inhuman spirit powerful enough to cloud Lorraine's sight is more than a match for me. (..)2016 The Conjuring 2