A Listener of the old school with a grid half full of non-words. Nothing wrong with that, but the theme is well-worn and I found the puzzle a bit tedious. It's probably very tough if one doesn't get the quote early, which I did by guessing the poet and the first three words from the four extra letters I had identified in the first batch of clues. It would also be very tough for someone without access to some pattern-matching crossword program. The poem is rather more interesting than the puzzle, in my opinion.
I can't see the point of a clue like 1d where we have a definition to a nine-letter word, which is not in itself thematic (and could be one of many) and wordplay to a four-letter word that is the grid entry. I did work out the longer word but I almost couldn't be bothered. In effect the longer answer has six unchecked letters, hardly indicative of a crossword.
However, to counterbalance that negativity, I will credit the setter with a very good grid that has some nice traps for the unwary.