Upper-class person of superior heredity, the tops! (4)
I believe the answer is:
posh
'upper-class' is the definition.
(I've seen this before)
'person of superior heredity the tops' is the wordplay.
'the tops' says to take the initial letters.
The initial letters of 'person of superior heredity' is 'POSH'.
(Other definitions for posh that I've seen before include "This 13 [SPICE]" , "Smart, stylish" , "refined" , "Elegant and fashionable" , "Smart - upper-class" .)