About to dip into novel but Hay Festival's here (8)
I believe the answer is:
bayreuth
'festival's here' is the definition.
(site of an annual music festival)
'about to dip into novel but hay' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'to dip into' means one lot of letters goes inside another.
'novel' is an anagram indicator (letters in a new or novel order).
'but'+'hay'='buthay'
'buthay' is an anagram of 'bayuth'.
're' going within 'bayuth' is 'BAYREUTH'.
(Other definitions for bayreuth that I've seen before include "Rings witnessed here" , "Town in Bavaria associated with Wagner" , "Bavarian town associated with Wagner" , "Wagner festival town" , "Site of annual Wagner festival" .)