Guy in America, about 50, one rushing around (7)

I believe the answer is:

bustler

'one rushing around' is the definition.
(to bustle is to rush around)

'guy in america about 50' is the wordplay.
'guy in america' becomes 'buster' (US informal term for a man).
'about' means one lot of letters goes inside another.
'50' becomes 'l' (roman numeral).
'buster' going around 'l' is 'BUSTLER'.

(Another definition for bustler that I've seen is " Active person".)

I've seen this clue in The Times.

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