Hi Bunty, there are four 'books' from the unclued words. 1A is the first word of the 1st. There are three intervening 'books' that slot between these, so you go 1A to the word in the 3rd column (the 1st book) then there''s a missing book , then the unclued word in the 4th column to the unclued word in the 6th and so on, all sorted in alphabetical order.
The 4th book is a missing book, beginning with a word in the dictionary next to the unclued word in 6th column to a word in the dictionary next to unclued word in 7th (your RAN?).
Phew....err, hope that's clear ?