No-good silver-tongued weaselly type written up in book (8)
I believe the answer is:
libretto
'book' is the definition.
(I know that libretto is a type of book)
'no-good silver-tongued weaselly type written up' is the wordplay.
'no' suggests deleting specific letters.
'good' becomes 'g' (abbreviation).
'silver-tongued' becomes 'glib' (I've seen this in another clue).
'weaselly type' becomes 'otter'.
'written up' says the letters should be written in reverse.
'glib' with 'g' taken out is 'lib'.
'otter' backwards is 'retto'.
'lib'+'retto'='LIBRETTO'
'in' acts as a link.
(Other definitions for libretto that I've seen before include "Text set to music in opera" , "11 down book" , "Script for a musical drama" , "textbook" , "Opera's words" .)