The most common and most likely answer to this crossword clue is the 10 letter word FILTRATION
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result FILTRATION
Buddy explains!
The straight part
We know that "Straining" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case straining = filtration.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 FILTRATION mean?
FILTRATION noun- The act or process of filtering; the mechanical separation of a liquid from the undissolved particles floating in it.
- A totally ordered collection of subsets.