Illustration in book is central to revised perfection (12)
I believe the answer is:
frontispiece
'illustration in book' is the definition.
'frontispiece' can be an answer for 'illustration' (I've seen this before). I am unsure of the 'in book' bit.
'is central to revised perfection' is the wordplay.
'central to' means one lot of letters goes inside another (letters are inserted into the centre of the word).
'revised' indicates anagramming the letters.
'perfection' is an anagram of 'frontpiece'.
'is' inserted inside 'frontpiece' is 'FRONTISPIECE'.
Can you help me to learn more?
(Other definitions for frontispiece that I've seen before include "Plate" , "Illustration facing a book's title page" , "Picture at beginning of book" .)