have a clue

have a clue (third-person singular simple present has a clue, present participle having a clue, simple past and past participle had a clue)

1. (colloquial) To be knowledgeable about a topic or situation.
   • 2020 December 2, Paul Bigland, “My weirdest and wackiest Rover yet”, in Rail, page 68:

     I haven't booked, so I don't have a clue as to whether the service will be busy or not. Supposedly, reservations are compulsory, but I want to find out what would happen if you just turn up.

As a negative polarity item, it is chiefly used in the negative.

• clueful
• clueless