Single women enthralled by surrealist festival (6)
I believe the answer is:
diwali
'festival' is the definition.
(I've seen this before)
'single women enthralled by surrealist' is the wordplay.
'single' becomes 'i' (one).
'women' becomes 'w'.
'enthralled by' indicates putting letters inside ('enthral' can mean 'capture').
'surrealist' becomes 'dali' (Salvador Dali).
'i'+'w'='iw'
'iw' placed into 'dali' is 'DIWALI'.
(Other definitions for diwali that I've seen before include "Indian festival" , "Hindu festival of lights" , "Light festival" , "Festival in honour of Lakshmi" , "religious festival" .)