The most common and most likely answer to this crossword clue is the 14 letter word STRATIFICATION
I've seen this crossword clue in The Sunday Telegraph
S
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Buddy explains!
The straight part
We know that "Creating classes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case creating classes = stratification.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 STRATIFICATION mean?
STRATIFICATION noun- The process leading to the formation or deposition of layers, especially of sedimentary rocks
- A layering of musical texture
- The vertical layering of vegetation in a forest
- Society's categorization of people into socioeconomic strata