Rebellious, overweight Goth spurned onlooker (6)

I believe the answer is:

viewer

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

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

(Other definitions for viewer that I've seen before include "Review for TV watcher" , "Audience member" , "He surveys, or watches TV" , "One watching, eg, TV" , "Spectator" .)

I've seen this clue in The Irish Times.

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