Austere, rigorous (7)
I believe the answer is:
spartan
This clue is a double definition.
'austere' is the first definition.
(I know that austere can be written as spartan)
'rigorous' is the second definition.
(I've seen this before)
(Other definitions for spartan that I've seen before include "toughly-disciplined type" , "Bleak - rigorous - austere" , "Rather austere" , "Strictly disciplined" , "Not comfortable" .)