The most common and most likely answer to this crossword clue is the 6 letter word DRYING
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More clues leading to the result DRYING
Buddy explains!

The straight part
We know that "desertification?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case desertification? = drying.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 DRYING mean?
DRYING verb- To lose moisture.
- To remove moisture from.
- To be thirsty.
- To exhaust; to cause to run dry.
- For an actor to forget his or her lines while performing.
- The act of drying.
- A method of food preservation by removing water.