The most common and most likely answer to this crossword clue is the 8 letter word TRUTHFUL
I've seen this crossword clue in Financial Times
T
R
U
T
H
F
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L
More clues leading to the result TRUTHFUL
Buddy explains!

The straight part
We know that "Straight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case straight = truthful.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 TRUTHFUL mean?
TRUTHFUL adjective- Honest, and always telling the truth.
- Accurately depicting what is real.