The most common and most likely answer to this crossword clue is the 8 letter word SNEERING
I've seen this crossword clue in The Times
S
N
E
E
R
I
N
G
Buddy explains!

The straight part
We know that "Disdaining" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case disdaining = sneering.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 SNEERING mean?
SNEERING verb- To raise a corner of the upper lip slightly, especially in scorn
- To utter with a grimace or contemptuous expression; to say sneeringly.
- The act of one who sneers.