Not come across the poem before (not like you educated folks who quickly "guessed" it) but found it with a bit of digging and now just wavering on the last clue, 14a. I assume the Isle must be the famous exile Isle but can't get the wordplay.
Also, on to the thematic word. By "consecutive jumble", I assume I'm looking for the 11 letters in 6 clues but they are consecutive within each clue? I think I have a surplus letter in 1d and 3 letters in 39d? I can see possible surplus letters or words in 4, 8, 15, 19, 25.
Tricky. Any hints appreciated.