The most common and most likely answer to this crossword clue is the 9 letter word REVERSALS
I've seen this crossword clue in The Daily Telegraph
R
E
V
E
R
S
A
L
S
Buddy explains!

The straight part
We know that "setbacks" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case setbacks = reversals.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 REVERSALS mean?
REVERSALS noun- The state of being reversed.
- An instance of reversing.
- A change in fortune; a change from being successful to having problems.