The most common and most likely answer to this crossword clue is the 9 letter word ATTENTION
I've seen this crossword clue in The Times
A
T
T
E
N
T
I
O
N
More clues leading to the result ATTENTION
- Shelter received by people wanting new treatment
- Keen students pay this order to stand still
- What pupils should pay? A strain, by the sound of it
- 8! That’s early in the morning for some into raves
- Order given to soldiers to show care
- What a lecturer wants to be paid?
- Standing order, rigidly obeyed
- Army command to be rigidly obeyed
- What students must pay for special treatment
- Heed  military order
Buddy explains!
The straight part
We know that "treatment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case treatment = attention.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 ATTENTION mean?
ATTENTION noun- Mental focus.
- An action or remark expressing concern for or interest in someone or something, especially romantic interest.
- A state of alertness in the standing position.
- Used as a command to bring soldiers to the attention position.
- A call for people to be quiet/stop doing what they are presently doing and pay heed to what they are to be told or shown.