(from earlier) 10a The 'key' grows on something, and the final five words of the clue adapt the word immediately before them.
3d - 2 letters (slang) 'one'/me + abbrev reversed inside.
I agree that the poem is pretty dire but it served to provide a notable title later in the century. It took a while for all the pennies to drop but it proved to be an excellent challenge and a tour de force of construction from Ifor, to whom fulsome thanks.
Thanks I have it. And full grid.
Wow. I am imagining explaining the clue for 10a to my friends who don't do crosswords...even the definition is impenetrable!