Initiator of action involving port authority in dispute (9)
I believe the answer is:
plaintiff
'initiator of action' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'port authority in dispute' is the wordplay.
'port authority' becomes 'pla' (Port of London Authority).
'dispute' becomes 'tiff' (tiff is a kind of dispute).
'pla'+'in'+'tiff'='PLAINTIFF'
'involving' acts as a link.
Can you help me to learn more?
(Other definitions for plaintiff that I've seen before include "Person bringing a legal action" , "he goes to court" , "Complainant" , "One bringing legal case" , "Temporary disappearances of a heavenly body" .)