The most common and most likely answer to this crossword clue is the 9 letter word DWINDLING
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More clues leading to the result DWINDLING
Buddy explains!

The straight part
We know that "Getting less" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case getting less = dwindling.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 DWINDLING mean?
DWINDLING verb- To decrease, shrink, diminish, reduce in size or intensity.
- To fall away in quality; degenerate, sink.
- To lessen; to bring low.
- To break up or disperse.
- A gradual reduction to nothing.
- Declining; growing less