The most common and most likely answer to this crossword clue is the 9 letter word ANTI-LOCK
I've seen this crossword clue in The Guardian
A
N
T
I
-
L
O
C
K
Buddy explains!
The straight part
We know that "As might be brakes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case as might be brakes = anti-lock.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 ANTI-LOCK mean?
ANTI-LOCK adjective- Preventing something from becoming stuck or jammed. Especially applies to anti-lock brakes, which are designed to continue rotating for better steering control while slowing the vehicle, rather than "locking" and causing the car to skid.