Soviet political prison (5)
I believe the answer is:
gulag
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">soviet political prison</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for gulag that I've seen before include "Labour camp for political prisoners" , "Soviet political prison system" , "Labour camp in the Soviet Union" , "place of detention" , "Soviet forced labour camp(s)" .)