Crossword Genius

One beat greatest boxer taken inside restaurant (7)

Ross

I believe the answer is:

italian

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

'one beat greatest boxer taken inside' is the wordplay.
'one' becomes 'I' (Roman numeral).
'beat' becomes 'tan' (I've seen this before).
'greatest boxer' becomes 'ali' (Muhammad Ali. I am not sure about the 'greatest' bit.).
'taken inside' is an insertion indicator.
'tan' placed around 'ali' is 'talian'.
'i'+'talian'='ITALIAN'

Can you help me to learn more?

(Other definitions for italian that I've seen before include "Person from Rome, say" , "Dante's tongue" , "In a tail (anag)" , "Romance language" , "This European is anti Lia, oddly" .)

I've seen this clue in The Sun.
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