The most common and most likely answer to this crossword clue is the 9 letter word TURNROUND
I've seen this crossword clue in The Sunday Telegraph
T
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More clues leading to the result TURNROUND
Buddy explains!

The straight part
We know that "reversal of fortune" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reversal of fortune = turnround.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.
Crossword Answer definitions
TURNROUND noun- (sometimes derogatory) An emigrant heading west on the Oregon Trail who gave up and turned back to the east.
- A section of honeycomb that is unfinished and returned to the hive.
- The act of turning to face in the other direction.
- A reversal of policy.
- The time required to carry out a task.
- A turnabout; a reversal of circumstances.
- A series of sketches of a character as seen from different angles.
- A cadence linking the end of a verse to the beginning of the next.
- The notation for the addition of a grace note above then below a given note.
- The scheduled shutdown of an industrial plant, such as an oil rig, for maintenance and testing.
- A contractual provision by which, if the studio elects to abandon a film project, the producer has a limited period in which to sell it elsewhere.
- Preparations for takeoff, such as loading and servicing.