It's nice being a toff (5)

I believe the answer is:

swell

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'toff' is the definition.
(wealthy or high-class person)

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

(Other definitions for swell that I've seen before include "Heave of sea; expand" , "Become larger in size" , "marvellous" , "Expand - great!" , "Bulge; a nob" .)

I've seen this clue in the Evening Standard.

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