Fitting appeal into litigating (7)
I believe the answer is:
suiting
'fitting' is the definition.
('suit' can be a synonym of 'fit')
'appeal into litigating' is the wordplay.
'appeal' becomes 'it' ('it' can mean something attractive or appealing).
'into' indicates putting letters inside.
'litigating' becomes 'suing' ('sue' can be a synonym of 'litigate').
'it' inserted inside 'suing' is 'SUITING'.
(Other definitions for suiting that I've seen before include "Pleasing; cloth for formal wear" , "Being acceptable to" .)