Excuse of being elsewhere (5)
I believe the answer is:
alibi
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">excuse of being elsewhere</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for alibi that I've seen before include "Defence used by an accused person" , "Excuse, in law" , "Defence of being elsewhere at time of crime" , "Story confirming innocence" , "Proof of absence" .)