Endless oriental holiday in spring (6)
I believe the answer is:
easter
'holiday in spring' is the definition.
'Easter' can be an answer for 'spring' (Easter is part of springtime). I'm not certain of the 'holiday in' bit.
'endless oriental' is the wordplay.
'endless' means to remove the last letter.
'oriental' becomes 'eastern' (synonyms).
'eastern' with its last letter taken away is 'EASTER'.
Can you help me to learn more?
(Other definitions for easter that I've seen before include "Christian celebration for Teresa" , "Card, egg or Island" , "Time to celebrate" , "festival time" , "Christian celebration at the end of Lent" .)