The side of justice (5)
I believe the answer is:
right
I believe this clue is a double definition.
'the side' is the first definition.
'justice' is the second definition.
(right is a kind of justice)
'of' is the link.
(Other definitions for right that I've seen before include "Accurate" , "Not left" , "OK?" , "Morally defensible" , "Morally good, justifiable or acceptable" .)