Outrage as a Guardian setter's reported (5)

I believe the answer is:

appal

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'outrage' is the definition.
(I know that outrage can be written as appal)

I can't explain the rest of the clue.

(Other definitions for appal that I've seen before include "Outrage" , "exhibiting dismay" , "Disgust" , "Cause to be unpleasantly surprised" , "Petrify" .)

I've seen this clue in The Guardian.

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