Go to court about source of rotten discharge, guaranteed success (4-4)
I believe the answer is:
sure-fire
'go to court about source of rotten' is the definition.
I can't tell whether this definition defines the answer.
'discharge guaranteed success' is the wordplay.
I cannot really understand how this works, but
'discharge' could be 'fire' (synonyms) and 'fire' is located in the answer.
'guaranteed' could be 'sure' (I've seen this in another clue) and 'sure' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sure-fire that I've seen before include "Certain of success" , "Dead cert" , "Infallible" , "Certain to succeed - a positive conflagration?" .)