The most common and most likely answer to this crossword clue is the 9 letter word DILIGENCE
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result DILIGENCE
Buddy explains!
The straight part
We know that "Coach" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coach = diligence.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 DILIGENCE mean?
DILIGENCE noun- Steady application; industry; careful work involving long-term effort.
- The qualities of a hard worker, including conscientiousness, determination, and perseverance.
- Carefulness.
- (19th century) A public stage-coach.
- The process by which persons, lands, or effects are seized for debt; process for enforcing the attendance of witnesses or the production of writings.