The most common and most likely answer to this crossword clue is the 4 letter word KATA
I've seen this crossword clue in The Times
K
A
T
A
Buddy explains!
The straight part
We know that "Japanese exercises" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case japanese exercises = kata.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 KATA mean?
KATA noun- Any of a sequence of positions and movements used in many martial arts.
- (in combination) A drop (in temperature).
- In a direction analogous to down, but along the additional axis added by the fourth dimension.
- (measuring instrument) A device consisting principally of an alcohol thermometer, used to measure air cooling power and, indirectly, small wind speeds in circulating air, by measuring the time taken for the temperature of the bulb of alcohol to make a specified drop (100° to 95°F).
- A kind of pastry in Armenia and some neighboring countries.