Deprive of strength (5)
I believe the answer is:
drain
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deprive of strength</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 drain that I've seen before include "Waste channel" , "Draw off U sewer" , "Make weak" , "Waste pipe" , "Exhaust (of liquid)" .)