The most common and most likely answer to this crossword clue is the 7 letter word MCENROE
I've seen this crossword clue in Independent
M
C
E
N
R
O
E
More clues leading to the result MCENROE
- Chaps eating cold caviar he served professionally
- Marilyn has church for old tennis player
- One known to question seriousness of court official?
- Tennis player — you could see me once with head of racket broken
- Mere con playing tennis champ
- Servants keeping cold eggs for one player here
- Serviceman or men gathered outside church
Buddy explains!

The straight part
We know that "One known to question seriousness of court official?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one known to question seriousness of court official? = mcenroe.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.