The most common and most likely answer to this crossword clue is the 9 letter word ANASTASIA
I've seen this crossword clue in Financial Times
A
N
A
S
T
A
S
I
A
More clues leading to the result ANASTASIA
- Three articles about secret police woman
- A continent invaded by endlessly mean old royal
- Famous Russian, as presented in Disney film, avoiding capital of France
- Perhaps a … a tsarina’s missing daughter in the end?
- A new sparkling wine to drink when with a Russian princess
- Film horrible short adult that’s incontinent
- Santa redirected to the East for last princess
- Incontinent, slovenly Santa probably murdered Grand Duchess!
- Perhaps a ... a tsarina's missing daughter in the end?
Buddy explains!

The straight part
We know that "old royal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old royal = anastasia.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.