Breathe out: breathe your last? (6)
I believe the answer is:
expire
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">breathe out</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that breathe out can be written as expire)</span><br/ ><br/ >'<span class="explanation-format__original">breathe your last?</span>' is the second definition.<br/ ><br/ ></span>
(Other definitions for expire that I've seen before include "Expel air or die" , "Breathe out or run out" , "Breathe out - die" , "Lose validity" , "Die, give out" .)