Common defense (5)
I believe the answer is:
alibi
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">common defense</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 alibi that I've seen before include "Making excuse" , "Proof of not being at the scene of the crime" , "Evidence one was elsewhere at time of crime" , "it may help you to get off" , "Plea of absence" .)