Defence of being elsewhere at the time of a crime (5)
I believe the answer is:
alibi
'defence of being elsewhere at the time of a crime' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for alibi that I've seen before include "Claim put to court" , "Suspect's excuse" , "excuse given" , "Defence against accusation - was seen elsewhere at the time" , "that gets him off the hook?" .)