The most common and most likely answer to this crossword clue is the 6 letter word ATHENS
I've seen this crossword clue in The Guardian
A
T
H
E
N
S
More clues leading to the result ATHENS
- Capital at that time invested in a Society
- Description of heart of classy city
- Capital in Asia then, Seoul
- Birthplace of Plato — as thus written?
- Capital letters reading across from left of keyboard?
- Like stocks subsequently to yield capital
- Capital letters from the outset, if spelling 32
- City seeing wild Thebans losing capital in Boeotia
- Does it suggest a coin from ancient times, and where one may be found?
- Ordering of essential bits of cash as foreign capital
Buddy explains!
The straight part
We know that "foreign capital" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case foreign capital = athens.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.