Distinctive attribute (8)
I believe the answer is:
hallmark
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">distinctive attribute</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 hallmark that I've seen before include "Distinctive attribute" , "Goldsmith's stamp" , "Distinguishing characteristic - indicates standard of gold, silver etc." , "Assay stamp" , "Stamp of authority" .)