The most common and most likely answer to this crossword clue is the 10 letter word DEFILEMENT
I've seen this crossword clue in Financial Times
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More clues leading to the result DEFILEMENT
Buddy explains!

The straight part
We know that "pollution" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pollution = defilement.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 DEFILEMENT mean?
DEFILEMENT noun- The act of defiling.
- The state of being defiled.
- The protection of the interior walls of a fortification from enfilading fire, as by covering them, or by a high parapet on the exposed side.