Tapering flag (6)
I believe the answer is:
pennon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tapering flag</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 pennon that I've seen before include "tapered flag" , "Streamer on a lance" , "Long flag, often tapering" , "Flag carried by 9 across" , "Small triangular flag" .)