St Andrew's cross (7)
I believe the answer is:
saltire
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">st andrew's cross</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 saltire that I've seen before include "Diagonal cross (heraldry)" , "X-shaped cross" , "Scottish cross" , "Cross like St Andrew's" , "Heraldic cross" .)