In boat captain initially lost authority (6)

I believe the answer is:

oracle

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

I don't understand how the remainder of the clue works.

(Other definitions for oracle that I've seen before include "Prophetic priest/priestess" , "Soothsayer" , "Seer" , "Source of divine advice" , "Person regarded as source of knowledge, like old Greek prophet" .)

I've seen this clue in The Sun.

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