Greek box, light brown (7)
I believe the answer is:
spartan
'greek' is the definition.
(I know that Spartan is a type of greek)
'box light brown' is the wordplay.
'box' becomes 'spar' (spar can mean to box).
'light brown' becomes 'tan' (tan is a light brown colour).
'spar'+'tan'='SPARTAN'
(Other definitions for spartan that I've seen before include "Without comforts" , "Ascetic - ancient Greek" , "Very strict - austere" , "Indifferent to luxury" , "Lacking comfort or luxury" .)