Default, welsh (6)
I believe the answer is:
renege
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">default</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">welsh</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for renege that I've seen before include "In card games, revoke" , "South American cowboy" , "Change one's mind" , "Go back (on promise etc)" , "Fail to keep promise, or revoke in cards" .)