The most common and most likely answer to this crossword clue is the 13 letter word NOMENCLATURES
N
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M
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N
C
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S
Buddy explains!

The straight part
We know that "Names" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case names = nomenclatures.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 NOMENCLATURES mean?
NOMENCLATURES noun- A set of rules used for forming the names or terms in a particular field of arts or sciences.
- A set of names or terms.
- A name.