One-time nonconformist Welsh rite (9)

I believe the answer is:

erstwhile

I'm a little stuck... Click here to teach me more about this clue!

'one-time' is the definition.
(I know that one-time can be written as erstwhile)

'nonconformist welsh rite' is the wordplay.
'welsh rite' can be anagrammed to 'ERSTWHILE'.
However, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for erstwhile that I've seen before include "In the past" , "Formerly" , "Former, previous" , "Quondam" , "Former - list where (anag)" .)

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

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