They oppose prayer losing intro? (5)

I believe the answer is:

antis

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'they oppose' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for antis that I've seen before include "People who are opposed" , "They're opposed to" , "Opponents" , "the group voting no" , "They say no" .)

I've seen this clue in the Sydney Morning Herald.

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