The most common and most likely answer to this crossword clue is the 13 letter word INTERMEDIATES
I've seen this crossword clue in The Daily Telegraph
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Buddy explains!
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 INTERMEDIATES mean?
INTERMEDIATES noun- Anything in an intermediate position.
- An intermediary.
- Any substance formed as part of a series of chemical reactions that is not the end-product.