It’s fine being a toff (5)
I believe the answer is:
I believe this is a double definition.
'it's fine' is the first definition.
'a toff' is the second definition.
(wealthy or high-class person)
'being' is the link.
(Other definitions for swell that I've seen before include "Bulge; a nob" , "Excellent! - become larger" , "Balloon - movement of the sea's surface" , "Expand abnormally" , "Person of high social standing" .)