The most common and most likely answer to this crossword clue is the 7 letter word EUPHONY
I've seen this crossword clue in Financial Times
E
U
P
H
O
N
Y
Buddy explains!

The straight part
We know that "agreeable sound" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case agreeable sound = euphony.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 EUPHONY mean?
EUPHONY noun- A pronunciation of letters and syllables which is pleasing to the ear.
- Pleasant phonetic quality of certain words.