The most common and most likely answer to this crossword clue is the 9 letter word STAMPEDES
I've seen this crossword clue in The Guardian
S
T
A
M
P
E
D
E
S
Buddy explains!
The straight part
We know that "Careers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case careers = stampedes.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 STAMPEDES mean?
STAMPEDES noun- A wild, headlong scamper, or running away, of a number of animals; usually caused by fright; hence, any sudden flight or dispersion, as of a crowd or an army in consequence of a panic.
- A situation in which many people in a crowd are trying to go in the same direction at the same time.
- Any sudden unconcerted moving or acting together of a number of persons, as from some common impulse.