Angel having a flutter? (6)

I believe the answer is:

backer

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'angel' is the definition.
(angel can mean a financial backer)

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

(Other definitions for backer that I've seen before include "Sponsor" , "Financial supporter" , "'Supporter, usually provides finance (6)'" , "A supporter or a betting man" , "Person supporting another financially" .)

I've seen this clue in the Evening Standard.

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