Traveller's check
I believe the answer is:
rein
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">traveller's check</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 rein that I've seen before include "Controlling strap" , "Check; control" , "Horse controller" , "Slow-up" , "leading article?" .)