Feast I prepare for religious festival (6)
I believe the answer is:
fiesta
'for religious festival' is the definition.
(I've seen this before)
'feast i prepare' is the wordplay.
'prepare' is an anagram indicator (I've seen 'preparing' mean this (the same letters prepared differently)).
'feast'+'i'='feasti'
'feasti' is an anagram of 'FIESTA'.
(Other definitions for fiesta that I've seen before include "foreign holiday" , "Festivity, celebration" , "Religious festival in Hispanic communities" , "Elaborate public party, in Spain perhaps" , "religious celebration" .)