not have a clue

Từ điển Oxford Advanced Learner 8th

not have a ˈclue idiom
(informal)
1. to know nothing about sth or about how to do sth
•I don't have a clue where she lives.
2. (disapproving)to be very stupid
•Don't ask him to do it— he doesn't have a clue!
Main entry: ↑clue_idiom