The most common and most likely answer to this crossword clue is the 10 letter word GOVERNANCE
I've seen this crossword clue in The Guardian
G
O
V
E
R
N
A
N
C
E
Buddy explains!
The straight part
We know that "Ruling" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ruling = governance.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 GOVERNANCE mean?
GOVERNANCE noun- The process, or the power, of governing; government or administration.
- The specific system by which a political system is ruled.
- The group of people who make up an administrative body.
- The state of being governed.
- Accountability for consistent, cohesive policies, processes and decision rights.