The most common and most likely answer to this crossword clue is the 9 letter word MARGRAVES
I've seen this crossword clue in The Daily Telegraph
M
A
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Buddy explains!
The straight part
We know that "Foreign noblemen" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case foreign noblemen = margraves.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 MARGRAVES mean?
MARGRAVES noun- A feudal era military-administrative officer of comital rank in the Carolingian empire and some successor states, originally in charge of a border area.
- A hereditary ruling prince in certain feudal states of the Holy Roman Empire and elsewhere; the titular equivalent became known as marquis or marquess.