The most common and most likely answer to this crossword clue is the 1 plus 3 plus 2 plus 6 letter word A YEN TO TRAVEL
I've seen this crossword clue in The Daily Telegraph
A
Y
E
N
T
O
T
R
A
V
E
L
Buddy explains!
The straight part
We know that "Those having it won’t get far in Japan" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case those having it won’t get far in japan = a yen to travel.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.