The most common and most likely answer to this crossword clue is the 10 letter word CONDESCEND
I've seen this crossword clue in The Daily Telegraph
C
O
N
D
E
S
C
E
N
D
Buddy explains!
The straight part
We know that "Speak haughtily" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case speak haughtily = condescend.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 CONDESCEND mean?
CONDESCEND verb- To come down from one's superior position; to deign (to do something).
- To treat (someone) as though inferior; to be patronizing (toward someone); to talk down (to someone).
- (possibly nonstandard) To treat (someone) as though inferior; to be patronizing toward (someone); to talk down to (someone).
- To consent, agree.
- To come down.