A particular environment or walk of life (6)
I believe the answer is:
sphere
I believe this is a double definition.
'a particular environment' is the first definition.
(I've seen this before)
'walk of life' is the second definition.
(I've seen this in another clue)
(Other definitions for sphere that I've seen before include "Round object" , "Globe or ball" , "Vault of heaven" , "All-rounder" , "Round shape" .)