The most common and most likely answer to this crossword clue is the 6 letter word RULING
I've seen this crossword clue in Financial Times
R
U
L
I
N
G
More clues leading to the result RULING
- ...governing is upsetting, very loudly being dismissed
- Decision made by linesman?
- Judicial decision–making lines on page
- Regulation characterising a party in power?
- Umpire’s decision in game — a catch in the deep?
- No longer secure about love returned, requiring decision from judge
- Sovereign decree
- One way of underlining decision
- . Predominant decision
- Making a straight decision?
Buddy explains!

The straight part
We know that "Regulation/characterising a party in power" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case regulation/characterising a party in power = ruling.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 RULING mean?
RULING verb- To regulate, be in charge of, make decisions for, reign over.
- To excel.
- To mark (paper or the like) with rules (lines).
- To decide judicially.
- To establish or settle by, or as by, a rule; to fix by universal or general consent, or by common practice.
- To revel.
- An order or a decision on a point of law from someone in authority.
- That rules; predominant; chief; reigning; controlling.