Half a pair (3)
I believe the answer is:
one
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">half a pair</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for one that I've seen before include "This is singular" , "Unity" , "Single person or thing" , "Sole; identical" , "Unit" .)