The most common and most likely answer to this crossword clue is the 7 letter word HELLCAT
I've seen this crossword clue in Independent
H
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C
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More clues leading to the result HELLCAT
- Battle-axe that man will throw up
- Mistakenly call the malignant hag
- Spiteful person — he will shortly act badly
- Whip under the nether regions, as virago
- Spiteful person‘s coercive pressure trapping leaders of limited liability company
- Unpleasant female's violent act after ordeal
- Mistakenly call the spiteful person?
Buddy explains!

The straight part
We know that "malignant hag" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case malignant hag = hellcat.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 HELLCAT mean?
HELLCAT noun- A witch.
- A spiteful and violent person, especially a woman.