Concluded a lawsuit in capital (5,4)
I believe the answer is:
upper case
'capital' is the definition.
(synonyms)
'concluded a lawsuit' is the wordplay.
'concluded' becomes 'upper' (I can't explain this - if you can you should believe this answer much more).
'a lawsuit' becomes 'case' (a legal case).
'upper'+'case'='UPPER-CASE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for upper case that I've seen before include "used to begin sentence" , "(capitals here, please)" , "Capital letters like THESE" , "UNISON is in it!" , "LSD, but not pot, is in this" .)