Information on tax swells (6)
I believe the answer is:
gentry
'swells' is the definition.
(swell can mean an upper-class person)
'information on tax' is the wordplay.
'information' becomes 'gen' (gen can informally mean information).
'on' says to put letters next to each other.
'tax' becomes 'try' (I've seen this in another clue).
'gen'+'try'='GENTRY'
(Other definitions for gentry that I've seen before include "people of breeding show" , "Class of society" , "Privileged classes" , "aristocrats" , "(Upper class) people" .)