The most common and most likely answer to this crossword clue is the 6 letter word TEMPEH
T
E
M
P
E
H
Buddy explains!
The straight part
We know that "what makes some Japanese nosy (6)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what makes some japanese nosy (6) = tempeh.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 TEMPEH mean?
TEMPEH noun- An Indonesian food made from partially-cooked fermented soybeans, mixed with a fungus (Rhizopus oligosporus).