Crank (3)
(Other definitions for rev that I've seen before include "One turn of an engine, in short" , "Run (engine) quickly" , "Speed up engine (colloq.)" , "Clergyman, or woman (abbr)" , "Motor rotation, in short" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crank</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for kook that I've seen before include "Palindrome for eccentric person - in America" , "Eccentric person (sl.)" , "Crazy" , "US weirdo" .)