English idiot ruined new book (7)
I believe the answer is:
edition
'book' is the definition.
'english idiot ruined new' is the wordplay.
'english' becomes 'E' (abbreviation).
'ruined' is an anagram indicator.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'idiot' is an anagram of 'ditio'.
'e'+'ditio'+'n'='EDITION'
(Other definitions for edition that I've seen before include "I don tie (anag.)" , "I die not (anag)" , "Something impressed" , "Number of copies printed at one time" , "Particular form of a book" .)