Taken to court, last of source material (5)
I believe the answer is:
suede
'material' is the definition.
(I've seen this before)
'taken to court last of source' is the wordplay.
'taken to court' becomes 'sued' ('sue' can be a synonym of 'take to court').
'last of' suggests the final letters.
The final letter of 'source' is 'e'.
'sued'+'e'='SUEDE'
(Other definitions for suede that I've seen before include "unprepared material" , "Fabric" , "Hide from kids" , "Soft, velvety leather" , "leather material" .)