The most common and most likely answer to this crossword clue is the 8 letter word COACHING
I've seen this crossword clue in Financial Times
C
O
A
C
H
I
N
G
More clues leading to the result COACHING
Buddy explains!

The straight part
We know that "Instruction" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case instruction = coaching.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 COACHING mean?
COACHING verb- To train.
- To instruct; to train.
- To study under a tutor.
- To travel in a coach (sometimes coach it).
- To convey in a coach.
- The process by which someone is coached or tutored; instruction.