Ruling about reactionary in court not to our liking! (9)
I believe the answer is:
repugnant
'not to our liking' is the definition.
'ruling about reactionary in court' is the wordplay.
'ruling' becomes 'regnant' (as in a queen regnant, a queen who rules by birth).
'about' indicates putting letters inside.
'reactionary' is a reversal indicator (reactions happen in the opposite direction).
'in court' becomes 'up'.
'up' in reverse letter order is 'pu'.
'regnant' placed around 'pu' is 'REPUGNANT'.
(Other definitions for repugnant that I've seen before include "Very unwelcome" , "Abhorrent" , "Nasty" , "revolting" , "vile" .)