Magazine filler (6)
I believe the answer is:
insert
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">magazine filler</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 insert that I've seen before include "Place in between other things" , "supplement" , "Put something inside something else" , "Introduce, put in" , "Put in; enclosure" .)