Measuring stick (5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">measuring stick</span>' is the definition.<br/ ><span class="explanation-format__explanation">(ruler is a kind of measuring stick)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ruler that I've seen before include "Person in authority" , "Straight edge; monarch" , "Person in charge of country" , "Potentate" , "Stationery item" .)
(Other definitions for gauge that I've seen before include "Adjudge" , "Rail track width" , "Measure(r)" , "Measure - estimate" , "standard size" .)