It's not evident the plaintiff has a quarrel (4)
I believe the answer is:
tiff
'a quarrel' is the definition.
(informal term for an argument)
'it's not evident the plaintiff' is the wordplay.
'it's not' indicates named letters should be taken away.
'evident' becomes 'plain' (synonyms).
'plaintiff' with 'plain' removed is 'TIFF'.
'has' acts as a link.
(Other definitions for tiff that I've seen before include "Mild quarrel" , "Lovers' row" , "Slight quarrel" , "Minor squabble" , "A spat or small row" .)