Obscure book, not complete enticement (4)
I believe the answer is:
blur
'obscure' is the definition.
(synonyms)
'book not complete enticement' is the wordplay.
'book' becomes 'b' (abbreviation for book).
'not complete' means to remove the last letter.
'enticement' becomes 'lure' (lure is a kind of enticement).
'lure' with its final letter taken away is 'lur'.
'b'+'lur'='BLUR'
(Other definitions for blur that I've seen before include "Make less distinct" , "Pop group; make unclear" , "Fuzzy image" , "Make or become indistinct" , "Out-of-focus sight" .)