The most common and most likely answer to this crossword clue is the 6 letter word NUTTER
I've seen this crossword clue in The Daily Telegraph
N
U
T
T
E
R
More clues leading to the result NUTTER
Buddy explains!
The straight part
We know that "crackpot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case crackpot = nutter.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 NUTTER mean?
NUTTER noun- A person who gathers nuts.
- (sometimes derogatory) An eccentric, insane, crazy or reckless person.
- Nut butter