Used to celebrate Unionist politician standing by husband amid court case (9)
I believe the answer is:
triumphal
'used to celebrate unionist' is the definition.
I can't judge whether this definition defines the answer.
'politician standing by husband amid court case' is the wordplay.
'politician standing' becomes 'ump' (I can't justify this - if you can you should give a lot more credence to this answer).
'by' means one lot of letters go next to another.
'husband' becomes 'h' (abbreviation).
'amid' means one lot of letters goes inside another.
'court case' becomes 'trial' (a trial in court).
'ump'+'h'='umph'
'umph' put into 'trial' is 'TRIUMPHAL'.
Can you help me to learn more?
(Other definitions for triumphal that I've seen before include "Celebrating a victory" , "Exultant" , "Type of arch (as in Paris)" , "Exulting in success" , "Victorious" .)