Text at top of page (6)
I believe the answer is:
header
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">text at top of page</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for header that I've seen before include "Lines at top of page" , "Line at top of each page of a document" , "Line of text indicating what the passage below it is about" , "Text at top of page" , "One way to get a goal in football" .)