The most common and most likely answer to this crossword clue is the 4 plus 5 letter word LINE JUDGE
I've seen this crossword clue in The Guardian
L
I
N
E
J
U
D
G
E
Buddy explains!
The straight part
We know that "Official knowing the ins and outs of court?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case official knowing the ins and outs of court? = line judge.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.