### Clue: A lack of facilities set back Glastonbury, some say (6)
### Answer: AVALON 
 ### Explanation: Definition: Glastonbury, some say
 A + **reversal of**(… set back) [NO LAV] (no lavatory;a lack of toilet facilities).
Defn: What some claimed to be the burial site of King Arthur and his Queen, Avalon.
The surface reading could be said to be true of the Glastonbury Festival?