The most common and most likely answer to this crossword clue is the 9 letter word GUARDRAIL
I've seen this crossword clue in Financial Times
G
U
A
R
D
R
A
I
L
More clues leading to the result GUARDRAIL
Buddy explains!

The straight part
We know that "Safety barrier" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case safety barrier = guardrail.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 GUARDRAIL mean?
GUARDRAIL noun- A rail set alongside a dangerous place in order to improve safety.