Obscure book gets the usual spiel on the cover (5)
I believe the answer is:
blurb
'the usual spiel on the cover' is the definition.
(text on the back cover of a book)
'obscure book' is the wordplay.
'obscure' becomes 'blur' (both can mean to vague or indistinct).
'book' becomes 'b' (abbreviation for book).
'blur'+'b'='BLURB'
'gets' acts as a link.
(Other definitions for blurb that I've seen before include "Promotional statement on a book's dust jacket" , "A book's puff" , "Book endorsement" , "Publisher's promotional description" , "Publisher's descrtion of book" .)