Can't see why people are having such trouble with 19 - it's a syndrome that comes up with google. 14 is a proper word if you spell the Japanese art right (which I didn't to start with ...)
Chambers defines acronym as "a word formed from or based on initial letters or syllables of other words ..." therefore might not 13a be the referred to acronym?
Following your tips, I now have a completed grid. It doesn’t affect the solution, but the choice of acronym is between 13 and 19; because 19 is also a noun, I would go for 13.