The most common and most likely answer to this crossword clue is the 7 letter word EMPIRES
I've seen this crossword clue in The Daily Telegraph
E
M
P
I
R
E
S
More clues leading to the result EMPIRES
Buddy explains!
The straight part
We know that "rules" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rules = empires.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 EMPIRES mean?
EMPIRES noun- A political unit, typically having an extensive territory or comprising a number of territories or nations (especially one comprising one or more kingdoms) and ruled by a single supreme authority.
- A political unit ruled by an emperor or empress.
- A group of states or other territories that owe allegiance to a foreign power.
- An expansive and powerful enterprise under the control of one person or group.
- (Absolute) control, dominion, sway.