The most common and most likely answer to this crossword clue is the 10 letter word CATEGORISE
I've seen this crossword clue in The Daily Telegraph
C
A
T
E
G
O
R
I
S
E
More clues leading to the result CATEGORISE
Buddy explains!

The straight part
We know that "order" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case order = categorise.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 CATEGORISE mean?
CATEGORISE verb- To assign a category; to divide into classes.