Severely simple (7)
I believe the answer is:
austere
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">severely simple</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for austere that I've seen before include "'Spartan, simple (7)'" , "Severe, ascetic" , "Stern or very plain" , "Serious" , "Plain, cold" .)