The most common and most likely answer to this crossword clue is the 7 letter word TAINTED
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Buddy explains!
The straight part
We know that "Polluted" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case polluted = tainted.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 TAINTED mean?
TAINTED verb- To contaminate or corrupt (something) with an external agent, either physically or morally.
- To spoil (food) by contamination.
- To be infected or corrupted; to be touched by something corrupting.
- To be affected with incipient putrefaction.
- To mark (a variable) as unsafe, so that operations involving it are subject to additional security checks.
- To invalidate (a share capital account) by transferring profits into it.
- To damage, as a lance, without breaking it; also, to break, as a lance, but usually in an unknightly or unscientific manner.
- To hit or touch lightly, in tilting.
- To thrust ineffectually with a lance.
- Corrupted or filled with imperfections.
- (of data) Originating from an untrusted source.