Description of book written by rock band (5)
I believe the answer is:
blurb
'description' is the definition.
(I have seen 'Promotional description' mean 'blurb' so perhaps 'description' could also mean 'blurb')
'book written by rock band' is the wordplay.
'book' becomes 'b' (abbreviation for book).
'written by' says to put letters next to each other.
'rock band' becomes 'blur' (I've seen this before).
'b' put after 'blur' is 'BLURB'.
'of' is the link.
(Other definitions for blurb that I've seen before include "words on jacket?" , "Fulsome advertising matter" , "Book endorsement" , "Advertising spiel" , "Brief commendatory advertisement" .)