Feature of Piccadilly? Its not included in tours (6)

I believe the answer is:

circus

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'feature' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

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

Can you help me to learn more?

(Other definitions for circus that I've seen before include "entertaining show" , "'Travelling company of clowns, acrobats etc (6)'" , "Tented entertainment" , "Roundabout for the animal acts" , "Show - where traffic goes round" .)

I've seen this clue in The Daily Mail.

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