The most common and most likely answer to this crossword clue is the 15 letter word DESERTIFICATION
I've seen this crossword clue in The Times
D
E
S
E
R
T
I
F
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C
A
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N
More clues leading to the result DESERTIFICATION
Buddy explains!
The straight part
We know that "a loss of living things" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a loss of living things = desertification.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 DESERTIFICATION mean?
DESERTIFICATION noun- Process by which a geographic region becomes a desert. The change may result from natural changes in climate or by human activity.