The most common and most likely answer to this crossword clue is the 11 letter word TIE-BREAKER
T
I
E
-
B
R
E
A
K
E
R
Buddy explains!
The straight part
We know that "one producing a definite result at court" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one producing a definite result at court = tie-breaker.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 TIE-BREAKER mean?
TIE-BREAKER noun- Something that is used to pick a winner from a tied situation.