Spartan, simple (7)
I believe the answer is:
austere
I believe this is a double definition.
'spartan' is the first definition.
(I know that spartan can be written as austere)
'simple' is the second definition.
(I've seen this in another clue)
(Other definitions for austere that I've seen before include "Severe in manner" , "Stern, severe" , "Severe; lacking luxuries" , "Grim - USA tree (anag)" , "Sure eat up and become without luxury" .)