The most common and most likely answer to this crossword clue is the 13 letter word MULTICULTURAL
I've seen this crossword clue in The Daily Telegraph
M
U
L
T
I
C
U
L
T
U
R
A
L
Buddy explains!
The straight part
We know that "Showing diversity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case showing diversity = multicultural.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 MULTICULTURAL mean?
MULTICULTURAL adjective- Relating or pertaining to several different cultures.