The most common and most likely answer to this crossword clue is the 10 letter word ANTICLIMAX
I've seen this crossword clue in The Daily Telegraph
A
N
T
I
C
L
I
M
A
X
More clues leading to the result ANTICLIMAX
- Old buffoon unknown outside capital is let-down
- Cross after anarchic act in capital leads to disappointment
- Soldier, one hundred and ten, touring city that’s not as good as expected
- Coming out badly in tax claim is let-down
- Claim tax in crooked endeavour that ends in disappointment
- Not in favour of reaching the top – what a let down!
- Against short cut with most disappointing conclusion
Buddy explains!
The straight part
We know that "disappointment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case disappointment = anticlimax.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 ANTICLIMAX mean?
ANTICLIMAX noun- A failed or reverse climax, particularly: