Lawsuit involving bishop of a clan (6)
I believe the answer is:
tribal
'of a clan' is the definition.
(I've seen this before)
'lawsuit involving bishop' is the wordplay.
'lawsuit' becomes 'trial' (I can't justify this - if you can you should give a lot more credence to this answer).
'involving' means one lot of letters goes inside another.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'trial' enclosing 'b' is 'TRIBAL'.
Can you help me to learn more?
(Other definitions for tribal that I've seen before include "Relating to groups with strong loyalties" , "Of a particular group" , "Like many primitive societies" , "concerning clan" , "Of a traditional social group" .)