Force unit (4)
I believe the answer is:
dyne
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">force unit</span>' is the definition.<br/ ><span class="explanation-format__explanation">(dyne is a kind of force unit)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dyne that I've seen before include "Unit of force" , "physics unit" .)