The most common and most likely answer to this crossword clue is the 9 letter word SPELLINGS
I've seen this crossword clue in The Daily Telegraph
S
P
E
L
L
I
N
G
S
Buddy explains!
The straight part
We know that "what distinguishes them?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what distinguishes them? = spellings.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 SPELLINGS mean?
SPELLINGS noun- The act, practice, ability, or subject of forming words with letters, or of reading the letters of words; orthography.
- The manner of spelling of words; correct spelling.
- A specific spelling of a word.
- A spelling test or spelling bee.