The most common and most likely answer to this crossword clue is the 8 letter word GORMLESS
I've seen this crossword clue in The Guardian
G
O
R
M
L
E
S
S
More clues leading to the result GORMLESS
Buddy explains!

The straight part
We know that "not having a clue" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not having a clue = gormless.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GORMLESS mean?
GORMLESS adjective- (of a person) Lacking intelligence, sense or understanding; foolish.