Instrument played using circular breathing / THU 10-15-20 / Language that gave us spunk slogan / Rebellion 1808 uprising in New South Wales / Autobahn hazard

Constructor: Lindsey Hobbs

Relative difficulty: Medium (high 5s)

THEME: DOWN UNDER (55A: Nickname for 18-Across, and a hint to how four answers in this puzzle are to be entered) — themers are all associated with AUSTRALIA (18A: Locale suggested by this puzzle's theme) and are entered in such a way that the answer turns first "down" then "under" (i.e. the answers fold back underneath themselves):

Theme answers:

• PLATY / SESUP (i.e. "platypuses")
• KANG / OORA (i.e. "kangaroo")
• VEGE / ETIM (i.e. "Vegemite")
• DIDGE / OODIR (i.e. "didgeridoo")

Word of the Day: Novelist Santha Rama RAU (47D) —

Santha Rama Rau (24 January 1923 – 21 April 2009) was an Indian-born American writer. [...] When India won its independence in 1947, Rama Rau's father was appointed as his nation's first ambassador to Japan. While in Tokyo, Japan, she met her future husband, an American, Faubion Bowers. After extensive traveling through Asia and a bit of Africa and Europe, the couple settled in New York City, New York. Rama Rau became an instructor in the English language faculty of Sarah Lawrence College, Bronxville, New York, in 1971, also working as a freelance writer. // She adapted the novel A Passage to India, with author E. M. Forster’s approval, for the theater. The play of the same name was produced for the Oxford Playhouse, Oxford, United Kingdom, moved to the West End in London, United Kingdom, in 1960 for 261 performances, and then on to Broadway in New York City where it was staged 109 times. It was adapted by John Maynard and directed by Waris Husseinfor BBC television's Play of the Month in 1965. Although the film rights originally required Rama Rau to write the screenplay, director David Lean found her draft unsatisfactory and was able to reject it, although she is still credited in the titles because he still used some of her dialogue. // Rama Rau is the author of Home to India, East of Home, This is India, Remember the House (a novel), My Russian Journey, Gifts of Passage, The Adventuress, (a novel),  View to the Southeast, and An Inheritance, as well as co-author (with Gayatri Devi) of A Princess Remembers: the memoirs of the Maharani of Jaipur. (wikipedia)

And a KOALA for good measure (31D: Dweller in a eucalyptus forest). Here's a Thursday where looking DOWN UNDER (i.e. looking at the revealer clue first) wouldn't have helped a damn bit, as the revealer points you to 18-Across and the 18-Across clue tells you nothing. So you've gotta get answers into the grid before you can begin to have even an inkling of what's going on, which is fine by me as I tend to plunge right into every puzzle, hacking away at what I can get until the theme just ... sort of ... shows itself. Today, it took a weird lot of time to do that. I made good progress, but for a long time just didn't know how to enter those themers. Would've picked it up much quicker, probably, if I just could've gotten TYPIFIED (5D: Embodied). Clue had me thinking of something much more ... corporeal, and without the "Y" or "P" I couldn't see it ... and without the "Y" or "P" I also couldn't see PLATY/PUSES, though, honestly I didn't stop to think about it too much. Again, I tend to plow ahead. It's not clear to me if stopping to think about PLATY/PUSES would've paid off or just been a time suck. My general philosophy is if you get stuck, even a little, and you can move on, move on. I think the first themer I tumbled to was VEGE/MITE, which was hard because there was no reference to AUSTRALIA in the clue, and nothing at all referring to VEGE/MITE's unique look / texture / taste. Just "brand of sandwich spread" ... yikes. And we not only eat VEGE/MITE in this household, we once stockpiled it when we learned our grocery store was going to stop carrying it (they've since reversed course on this decision, thank god). Anyway, once you get the trick, the puzzle is not hard—typical Thursday, in that regard. And, much to my surprise and delight, getting the theme today made me feel like the struggle was worth it—a simple and very elegant expression of the revealer phrase. A "Huh, cool" rather than [shrug] or "ugh, really?"