The most common and most likely answer to this crossword clue is the 5 letter word DUNNO
I've seen this crossword clue in The Times
D
U
N
N
O
More clues leading to the result DUNNO
- Pass notes for couple to hold
- Casually pass dark horse with raised leg
- I'm Sorry I haven't a Clue team full of news
- I’m in the dark brown number
- Pair taking in two points haven’t a clue
- Carried upside-down by matron nude, I’m clueless!
- Cargo of contraband unnoticed? Search me
- Sorry, I can’t help you up on horse first
- Director of international body has power to come up and search me
- Pair guarding terminals in Newhaven search me
Buddy explains!

The straight part
We know that "Pass" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pass = dunno.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 DUNNO mean?
DUNNO noun- An utterance of the word dunno.