The most common and most likely answer to this crossword clue is the 6 letter word ADVISE
I've seen this crossword clue in Financial Times
A
D
V
I
S
E
Buddy explains!

The straight part
We know that "Guide" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case guide = advise.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 ADVISE mean?
ADVISE verb- To give advice to; to offer an opinion to, as worthy or expedient to be followed.
- To recommend; to offer as advice.
- To give information or notice to; to inform or counsel; — with of before the thing communicated.
- To consider, to deliberate.
- To look at, watch; to see.
- To consult (with).