Ancient letter (4)
I believe the answer is:
rune
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ancient letter</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 rune that I've seen before include "Mystic symbol" , "Ancient symbol" , "Mysterious character" , "Old alphabet letter" , "Ancient character" .)