Clue: 17's line suggesting tours in Abbey should be organised (1,8,6,2,4)
Answer: A TERRIBLE BEAUTY IS BORN
Explanation: Definition: 17's line
"Tours in Abbey" is an anagram of BEAUTY IS BORN. The line is from Yeats's Easter, 1916, commemorating the Easter Rising in Ireland on 24 April 1916. I think I vaguely knew it, but was held up by carelessly assuming that it was going to be by Kipling rather than Yeats