The most common and most likely answer to this crossword clue is the 9 letter word HEARTLESS
I've seen this crossword clue in Independent
H
E
A
R
T
L
E
S
S
More clues leading to the result HEARTLESS
- Lass there, awfully cruel
- Later she’s horribly cruel
- Cold gas, natural
- Cold about right?
- Callous as Doris would become after Rex left
- Cruel as a pack of three suits?
- The Parisian wears suit when cold
- Cruel Nazi leader impounds the French paintings first
- Cold as shelter in ruinous condition
- Cruel to let shares crash
Buddy explains!

The straight part
We know that "Callous" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case callous = heartless.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 HEARTLESS mean?
HEARTLESS adjective- Without courage; fearful, cowardly.
- Listless, unenthusiastic.
- Without a physical heart.
- Without feeling, emotion, or concern for others; uncaring.