Midriffs rejected as obscene content (4)

I believe the answer is:

smut

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'content' is the definition.
(I know that smut is a type of content)

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

Can you help me to learn more?

(Other definitions for smut that I've seen before include "(Speck) of dirt" , "Obscene filth" , "Dirt or pornography" , "Bit of soot or dirty talk" , "Dirty stuff" .)

I've seen this clue in The Telegraph.

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