This religious holiday over, you’d have to stop (3)
I believe the answer is:
eid
'this religious holiday' is the definition.
(Islamic festival)
'over you'd have to stop' is the wordplay.
'over you'd have' shows that the letters should be reversed in order (if you reverse the letters you get something else).
'to stop' becomes 'die' (I've seen this in other clues).
'die' backwards is 'EID'.
(Other definitions for eid that I've seen before include "feast" , "religious festival" .)