Prison guard (6)
I believe the answer is:
warder
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">prison guard</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 warder that I've seen before include "keeper" , "Jailer" , "screw" , "Gaoler" , "Prison officer" .)