The most common and most likely answer to this crossword clue is the 8 letter word DEVIATED
I've seen this crossword clue in The Guardian
D
E
V
I
A
T
E
D
Buddy explains!
The straight part
We know that "Gone astray" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gone astray = deviated.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 DEVIATED mean?
DEVIATED verb- To go off course from; to change course; to change plans.
- To fall outside of, or part from, some norm; to stray.
- To cause to diverge.