Item made once only (3-3)
I believe the answer is:
one-off
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">item made once only</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for one-off that I've seen before include "Something unique" , "Made as single article, not repeated" , "Not repeated, being a single event or object" , "Not repeated or reproduced, a single thing" , "Made or done as a single thing, not repeated" .)