Linguistic unit
I believe the answer is:
phoneme
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">linguistic unit</span>' is the definition.<br/ ><span class="explanation-format__explanation">(phoneme is a kind of linguistic unit)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for phoneme that I've seen before include "Small bit of speech" , "Unit of spoken sound" , "distinctive sound" , "minimal piece of speech" .)