I'm a boorish lout and I'm very happy about it! (5)

I believe the answer is:

yahoo

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'it' is the definition.
The definition suggests a singular noun which matches the answer.

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

Can you help me to learn more?

(Other definitions for yahoo that I've seen before include "Brutish lout" , "Boorish lout (after Swift)" , "A Swiftian lout" , "Lout (in Gulliver's Travels)" , "expression of delight" .)

I've seen this clue in The Independent.

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