The most common and most likely answer to this crossword clue is the 7 letter word FAILURE
I've seen this crossword clue in The Guardian
F
A
I
L
U
R
E
More clues leading to the result FAILURE
- Regularly fear I invite disaster
- A Bit of Fry & Laurie, hit and miss
- After scratching of head, nothing penned by composer is a disappointment
- Female an attraction, one hugged miss
- A Bit of Fry and Laurie, broadcast in Turkey
- One left consumed by composer’s lack of success
- Fuel and air mixture results in breakdown
- Catastrophe if a rule’s broken
- If a rule’s broken?
- Fellow having trouble on Yorkshire river is a loser
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 = failure.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 FAILURE mean?
FAILURE noun- State or condition of not meeting a desirable or intended objective, opposite of success.
- An object, person or endeavour in a state of failure or incapable of success.
- Termination of the ability of an item to perform its required function; breakdown.
- Bankruptcy.