Endless oriental holiday (6)
I believe the answer is:
easter
'holiday' is the definition.
(Easter is a Christian holiday)
'endless oriental' is the wordplay.
'endless' means to remove the last letter.
'oriental' becomes 'eastern' (similar in meaning).
'eastern' with its last letter taken off is 'EASTER'.
(Other definitions for easter that I've seen before include "Card, egg or Island" , "Resurrection festival" , "Main Christian festival" , "festival time" , "Sort of tide" .)