Obscure book? This description might help (5)
I believe the answer is:
blurb
'this description might help' is the definition.
'blurb' can be an answer for 'description' (I have seen 'Promotional description' mean 'blurb' so perhaps 'description' could also mean 'blurb'). I am unsure of the remainder of the definition.
'obscure book?' is the wordplay.
'obscure' becomes 'blur' (both can mean to vague or indistinct).
'book?' becomes 'b' (abbreviation for book).
'blur'+'b'='BLURB'
Can you help me to learn more?
(Other definitions for blurb that I've seen before include "Advertising text" , "Publisher's book description" , "Advertising description praising something" , "Fulsome advertising matter" , "stuff on jacket" .)