Greeting Scottish banker and a regressively religious authority (9)

I believe the answer is:

ayatollah

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'religious authority' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for ayatollah that I've seen before include "High-ranking Shiite religious leader" , "Shiite leader, possibly in 10 across" , "Religious high-up" , "religious authority" , "Muslim leader" .)

I've seen this clue in The Independent.

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