Double-cross (6)
I believe the answer is:
betray
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">double-cross</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for betray that I've seen before include "26 [SELL]" , "Double-cross, sell out" , "Sell down the river" , "Reveal (intentionally or unintentionally)" , "Breach the trust of" .)