Judges, for example, to me must be united (4)
I believe the answer is:
book
'judges for example' is the definition.
(book of the Bible)
I cannot understand how the rest of the clue works.
(Other definitions for book that I've seen before include "Strict rules" , "Make a reservation" , "Reserve - bets taken on a race" , "Reading volume" , "Reserve - volume" .)