Revs the engine
I believe the answer is:
guns
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">revs the engine</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for guns that I've seen before include "Snug weapons?" , "Transportable armaments" , "Firearms" , "Bangers" .)