Dubious, spread-eagle pal scorned cleanse (8)

I believe the answer is:

degrease

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'cleanse' is the definition.
Both the answer and definition are verbs in their base form.
Maybe they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for degrease that I've seen before include "Remove oily substance from" , "Lose fat" , "Remove fat" , "Remove oily matter from" .)

I've seen this clue in The Irish Times.

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