The most common and most likely answer to this crossword clue is the 10 letter word MONARCHIES
M
O
N
A
R
C
H
I
E
S
Buddy explains!
The straight part
We know that "kingdoms" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case kingdoms = monarchies.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 MONARCHIES mean?
MONARCHIES noun- A government in which sovereignty is embodied within a single, today usually hereditary head of state (whether as a figurehead or as a powerful ruler).
- The territory ruled over by a monarch; a kingdom.
- A form of government where sovereignty is embodied by a single ruler in a state and his high aristocracy representing their separate divided lands within the state and their low aristocracy representing their separate divided fiefs.
- States based on a system of governance headed by a king or a queen.