Measuring sticks (6)
I believe the answer is:
rulers
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">measuring sticks</span>' is the definition.<br/ ><span class="explanation-format__explanation">(ruler is a kind of measuring stick)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rulers that I've seen before include "Sovereigns and marked sticks" , "Heads of government" , "Sovereigns etc" , "Straight sticks for governors" , "Strips with straight edge to measure" .)