The most common and most likely answer to this crossword clue is the 9 letter word PRINCIPLE
I've seen this crossword clue in Independent
P
R
I
N
C
I
P
L
E
More clues leading to the result PRINCIPLE
- Articulate first rule
- Canon making a royal take pill, oddly left out
- Dictator’s supreme rule
- Canon‘s in clipper at sea
- … original source of first of Patsy Clineremixes
- One place keeps royal member out, as a rule
- Basic standard the head voiced
- Standard of behaviour head teacher announced
- Truth from headteacher on the radio
- Sounds like the most important rule
Buddy explains!

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 PRINCIPLE mean?
PRINCIPLE noun- A fundamental assumption or guiding belief.
- A rule used to choose among solutions to a problem.
- (sometimes pluralized) Moral rule or aspect.
- A rule or law of nature, or the basic idea on how the laws of nature are applied.
- A fundamental essence, particularly one producing a given quality.
- A beginning.
- A source, or origin; that from which anything proceeds; fundamental substance or energy; primordial substance; ultimate element, or cause.
- An original faculty or endowment.
- To equip with principles; to establish, or fix, in certain principles; to impress with any tenet or rule of conduct.