Feast I prepared for a religious festival (6)
I believe the answer is:
fiesta
'for a religious festival' is the definition.
(I've seen this before)
'feast i prepared' is the wordplay.
'prepared' indicates anagramming the letters.
'feast'+'i'='feasti'
'feasti' anagrammed gives 'FIESTA'.
(Other definitions for fiesta that I've seen before include "Latin American celebration" , "Elaborate public party, in Spain perhaps" , "Holiday; carnival" , "foreign holiday" , "Saint's day; carnival" .)