One initiating a lawsuit in ugly dispute (9)
I believe the answer is:
plaintiff
'one initiating a lawsuit' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'ugly dispute' is the wordplay.
'ugly' becomes 'plain' (I've seen this before).
'dispute' becomes 'tiff' (tiff is a kind of dispute).
'plain'+'tiff'='PLAINTIFF'
'in' is the link.
Can you help me to learn more?
(Other definitions for plaintiff that I've seen before include "One bringing civil court case" , "one prompting action" , "Complainant" , "The one taking the court action" , "one in suit" .)