The most common and most likely answer to this crossword clue is the 10 letter word DISAPPROVE
I've seen this crossword clue in The Guardian
D
I
S
A
P
P
R
O
V
E
More clues leading to the result DISAPPROVE
Buddy explains!

The straight part
We know that "Look down on/Look down on" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case look down on/look down on = disapprove.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 DISAPPROVE mean?
DISAPPROVE verb- To condemn; to consider wrong or inappropriate; used with of.
- To refuse to approve; reject.
- To have or express an unfavorable opinion.