Soviet labour camp (5)
I believe the answer is:
gulag
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">soviet labour camp</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for gulag that I've seen before include "in restraint here?" , "Soviet camp system" , "place of detention" , "Russian prison and labour camp organisation" , "where state's enemies were held" .)