The most common and most likely answer to this crossword clue is the 11 letter word DIACRITICAL
I've seen this crossword clue in The Times
D
I
A
C
R
I
T
I
C
A
L
More clues leading to the result DIACRITICAL
Buddy explains!

The straight part
We know that "showing distinction" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case showing distinction = diacritical.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 DIACRITICAL mean?
DIACRITICAL noun- A diacritic (mark).
- Capable of distinguishing or of making a distinction.
- Of, pertaining to, or serving as a diacritic