have a clue

not have a clue

1. To not have even a remote grasp or understanding of something; to be hopelessly confused or ignorant about something. You'd expect the average citizen to struggle to explain the workings of government, but now it seems like even most politicians don't have a clue! You don't have a clue about how to talk to people, do you? When it comes to trigonometry, I just don't have a clue.
2. To be completely unaware of something. A: "Do you think Paul suspects that we're having a surprise party for him? B: "No, he doesn't have a clue!"
See also: clue, have, not
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

have a clue (about something)

Fig. to know anything about something; to have even a hint about someone or something. (Usually negative.) I don't have a clue about where to start looking for Jim. Why do you think I have a clue about Tom's disappearance?
See also: clue, have
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
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References in classic literature ?
As long as this man has no idea that anyone can have a clue there is some chance of securing him; but if he had the slightest suspicion, he would change his name, and vanish in an instant among the four million inhabitants of this great city.
Del Monte Foods, who conducted the survey, said most Americans admit they are not getting the daily recommendation of fruits and vegetables and "don't have a clue when it comes to understanding the new Dietary Guidelines for Americans".
"I did not have a clue what I wanted to do as a career, so I joined Three A's Pertemps Training.
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