Wow. 28a was my LOI too, but I managed to see it when I fed the crossers into Qat. But a wicked parse! My faves were 13, 14, 23, 6 ...Thanks, that was a tough one, Paul...
.... I think part of the problem is that 15d has two valid spellings, one ending ER and one RE and, if you choose wrong, well - good luck making sense of 28a! 😜
Thanks Brendan, now you say that, I remember that same device came up recently- have to remember it next time!
I did wonder if it came from first two words, but then what would the definition be?