The most common and most likely answer to this crossword clue is the 6 letter word REFUTE
I've seen this crossword clue in The Daily Telegraph
R
E
F
U
T
E
More clues leading to the result REFUTE
- Discredit official before cup tie? Only occasionally
- Deny official regular appearances in cup ties
- Reply exposing fallacy, using tenets extant ab initio
- Deny United tie voided by match official
- Deny official EU backing for intervention by leader of Tories
- Disprove match official beginning to unveil note
- Disprove of demolishing reef around Andaman and Nicobar, say
- Deny about glass having large split
Buddy explains!

The straight part
We know that "Deny" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deny = refute.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 REFUTE mean?
REFUTE verb- To prove (something) to be false or incorrect.
- To deny the truth or correctness of (something).