The most common and most likely answer to this crossword clue is the 9 letter word SASHAYING
I've seen this crossword clue in The Guardian
S
A
S
H
A
Y
I
N
G
Buddy explains!

The straight part
We know that "what Kate Moss was doing on the runway" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what kate moss was doing on the runway = sashaying.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 SASHAYING mean?
SASHAYING verb- To walk casually, showily or in a flirty manner; to strut, swagger or flounce.
- To chassé when dancing.
- To move sideways.