The most common and most likely answer to this crossword clue is the 10 letter word SCREENWASH
I've seen this crossword clue in The Guardian
S
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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 SCREENWASH mean?
SCREENWASH noun- A fluid used to clean the windscreen of a motor vehicle; windshield washer fluid.
- To sift sediment through open boxes with screens at the bottom, as a technique for finding microfossils.