Fluid removing heat (7)
I believe the answer is:
coolant
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fluid removing heat</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 coolant that I've seen before include "part of heat exchanger" , "Fluid circulating in an engine or reactor" , "One should stop overheating" , "Heat-removing fluid" , "One must lower the temperature" .)