The most common and most likely answer to this crossword clue is the 7 letter word OMITTED
I've seen this crossword clue in The Times
O
M
I
T
T
E
D
More clues leading to the result OMITTED
- Hand detected in reference work is overlooked
- Old hand English duke failed to mention
- Old hand editor’s passed over
- Failed to find “glove” in dictionary
- Didn’t include synonym for ‘hand’ in dictionary
- Excluded slang for ‘paw’ in large lexicographic work
- Left out dictionary opened by hand
- Forgot to include “glove” in dictionary
- . Failed to provide a hand in the dictionary
- Deleted word for “glove” in dictionary
Buddy explains!

The straight part
We know that "Failed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case failed = omitted.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 OMITTED mean?
OMITTED verb- To leave out or exclude.
- To fail to perform.
- To neglect or take no notice of.