The most common and most likely answer to this crossword clue is the 8 letter word DEROGATE
I've seen this crossword clue in The Guardian
D
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Buddy explains!
The straight part
We know that "to be disparaging" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to be disparaging = derogate.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 DEROGATE mean?
DEROGATE verb- To partially repeal (a law etc.).
- To detract from (something); to disparage, belittle.
- To take away (something from something else) in a way which leaves it lessened.
- To remove a part, to detract from (a quality of excellence, authority etc.).
- To act in a manner below oneself; to debase oneself.
- Debased