Local square surrounded by green (6)
I believe the answer is:
native
'local' is the definition.
(similar in meaning)
'square surrounded by green' is the wordplay.
'square' becomes 'T' (a T-Square is a technical drawing instrument).
'surrounded by' indicates putting letters inside.
'green' becomes 'naive' (green can mean naive or innocent).
't' inserted inside 'naive' is 'NATIVE'.
(Other definitions for native that I've seen before include "Indigenous, aboriginal" , "Indigenous person" , "Belonging to a particular place by birth" , "Local inhabitant" , "Son" .)