The most common and most likely answer to this crossword clue is the 11 letter word THOUGHTLESS
I've seen this crossword clue in The Sunday Telegraph
T
H
O
U
G
H
T
L
E
S
S
More clues leading to the result THOUGHTLESS
- What aging philosopher did, possibly, showing no consideration?
- Allowing head of treasury a smaller amount is inconsiderate
- Insensitive, albeit not as much following start of talks
- Reduced number of brain operations, being inconsiderate
- Not using care, yet temperature reduced
- Developing hot legs and tush, silly
Buddy explains!
The straight part
We know that "Not using care" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not using care = thoughtless.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 THOUGHTLESS mean?
THOUGHTLESS adjective- Marked by or showing lack of due thought or care; careless.
- Inconsiderate, inattentive.
- Lacking thought or consideration.