The most common and most likely answer to this crossword clue is the 9 letter word CRESCENDO
I've seen this crossword clue in The Times
C
R
E
S
C
E
N
D
O
More clues leading to the result CRESCENDO
- Sign when playing soccer badly, letting in goal
- Faith, involving short display of emotion, getting stronger
- Getting louder? Time to exit street party!
- Time to leave street party — it’s getting noisier!
- Steady growth caught and censored, unfortunately
- Endless fuss during part of Mass getting louder
- Belief about timeless perfume being a high point
- Soccer playing about to finish leading to increasing noise
- Philosophy capturing detailed scene’s climax
- Endless street party that’s getting louder
Buddy explains!

The straight part
We know that "getting stronger" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case getting stronger = crescendo.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 CRESCENDO mean?
CRESCENDO noun- An instruction to play gradually more loudly, denoted by a long, narrow angle with its apex on the left ( < ), by musicians called a hairpin.
- A gradual increase of anything, especially to a dramatic climax.
- The climax of a gradual increase.
- To increase in intensity; to reach or head for a crescendo.
- Gradually increasing in force or loudness.