The most common and most likely answer to this crossword clue is the 14 letter word DISAPPOINTMENT
I've seen this crossword clue in Independent
D
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More clues leading to the result DISAPPOINTMENT
- Sadness caused by sacking?
- Detective’s date is anticlimax
- Regret getting sink filled with juice and oily substance
- CID officer’s job leads to frustration
- Police officer’s position causes frustration
- Frustrating thing, redundancy process?
- Detective’s engagement must be a let-down
- With Director on top, is job a let-down?
- Day one’s date is a letdown
- Girl’s lotion, after application, leads to failure
Buddy explains!

The straight part
We know that "anticlimax" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case anticlimax = disappointment.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 DISAPPOINTMENT mean?
DISAPPOINTMENT noun- A feeling of sadness or frustration when a strongly held expectation is not met.
- A circumstance in which a strongly held expectation is not met.
- That which causes feelings of disappointment.