The most common and most likely answer to this crossword clue is the 7 letter word HATEFUL
I've seen this crossword clue in The Guardian
H
A
T
E
F
U
L
More clues leading to the result HATEFUL
- Nasty European immersed in ten gallons, perhaps
- Dreadful, dreadful fate. Stuck in Hull with no end in view
- Abominable flu spreading after heat wave
- The flu spreading round, Asian origin, is horrible
- The flu spreading around area is nasty
- Detestable! Headwear falls on spilt fuel
- Nasty head, as it were, seen round middle of wen
- Loathsome husband developed fault importing drug
Buddy explains!

The straight part
We know that "Nasty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nasty = hateful.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 HATEFUL mean?
HATEFUL adjective- Evoking a feeling of hatred.
- Dislikeable.
- Full of hatred.