Legal excuses (6)
I believe the answer is:
alibis
'legal excuses' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alibis that I've seen before include "Proofs accused was elsewhere at time of crime" , "Pleas of being elsewhere at the time of a crime" , "Defences of being elsewhere at the time of a crime" , "Proofs of absence from the scene of the crime" , "They're useful to have if accused of crimes" .)