The most common and most likely answer to this crossword clue is the 8 letter word SADISTIC
I've seen this crossword clue in The Guardian
S
A
D
I
S
T
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C
More clues leading to the result SADISTIC
- Cruel, miserable lives and habitual response
- Sadly it’s said cruel leader could be thus
- It’s said erroneously about having a love of cruelty
- Upset with one’s credit being curtailed – cruel!
- Painful, is it, turning second of screws?
- Miserable one with endless cane could be vicious
- Back as a girl with a cane endlessly cruel
Buddy explains!

The straight part
We know that "Cruel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cruel = sadistic.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 SADISTIC mean?
SADISTIC adjective- Delighting in or feeling pleasure from the pain or humiliation of others.
- Of behaviour which gives pleasure in the pain or humiliation of others.
- Causing a high degree of pain or humiliation.