Length, extent (4)
I believe the answer is:
span
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">length</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that span is a type of length)</span><br/ ><br/ >'<span class="explanation-format__original">extent</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I have seen 'Extent of 20 ' mean 'span' so perhaps 'extent' could also mean 'span')</span><br/ ><br/ ></span>
(Other definitions for span that I've seen before include "Team of two matched oxen" , "Distance or interval between two points" , "Go across" , "Stretch; traverse" , "Extent - 9 inches" .)