Island; linear measure (4)
I believe the answer is:
inch
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">island</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(inch can mean a small island)</span><br/ ><br/ >'<span class="explanation-format__original">linear measure</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(inch is a kind of linear measure)</span><br/ ><br/ ></span>
(Other definitions for inch that I've seen before include "The island is very small in length" , "... or not so long < , Celtic island" , "Move in tiny increments" , "One of a 2 down in a foot" , "A very little" .)