The most common and most likely answer to this crossword clue is the 8 letter word DAMNABLE
I've seen this crossword clue in The Guardian
D
A
M
N
A
B
L
E
More clues leading to the result DAMNABLE
- Hateful mother with capacity to conceal name
- Extremely clever, but hateful
- Infernal island, Napoleon’s first, and lunatic flipped
- Cursed island and Napoleon’s head cracked, flipped
- Revolutionary island with bananas interrupted by Nationalist offensive
- Bloody awful! Bad man mistreated heads of ladies' establishment
Buddy explains!

The straight part
We know that "hateful" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hateful = damnable.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 DAMNABLE mean?
DAMNABLE adjective- Capable of being damned
- Deserving of damnation