Accused's need (5)
I believe the answer is:
alibi
'accused's need' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alibi that I've seen before include "Evidence one was not at crime scene" , "Timely excuse" , "Legal proof of innocence" , "Court evidence showing one was elsewhere" , "Legal defence, plea" .)