The most common and most likely answer to this crossword clue is the 4 letter word OBIS
O
B
I
S
More clues leading to the result OBIS
Buddy explains!

The straight part
We know that "Japanese sashes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case japanese sashes = obis.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 OBIS mean?
OBIS noun- A form of folk magic, medicine or witchcraft originating in Africa and practised in parts of the Caribbean.
- A magician or witch doctor of the magic craft.
- A spell performed in the practice of the magic craft; an item associated with such a spell.
- A sash worn with a kimono.
- A strip of paper looped around a book or other product.