The most common and most likely answer to this crossword clue is the 6 letter word NAIRAS
I've seen this crossword clue in The Guardian
N
A
I
R
A
S
More clues leading to the result NAIRAS
Buddy explains!

The straight part
We know that "currency abroad" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case currency abroad = nairas.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 NAIRAS mean?
NAIRAS noun- The official currency of Nigeria, which replaced the pound in 1973; the principal denomination of the currency, equal to 100 kobo.