The most common and most likely answer to this crossword clue is the 4 letter word ACED
I've seen this crossword clue in The Guardian
A
C
E
D
More clues leading to the result ACED
- After a month, returned and got a hole in one
- One Derbyshire opener beaten by unplayable ball
- Gave excellent service to Ant at first, upsetting partner
- Served to perfection?
- Gave good service to one department
- Suffered discomfort leaving hotel that’s provided a good service?
- Beaten by a single stroke
- After top honour, duke worsted in court, in a way
- Seven years almost up, perhaps, served in exemplary fashion
- Ran, crossed the leader and defeated
Buddy explains!

The straight part
We know that "Gave excellent service" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gave excellent service = aced.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 ACED mean?
ACED verb- (US) To pass (a test, interviews etc.) perfectly.
- To win a point by an ace.
- To make an ace (hole in one).