Terrible lout's case - it has no chance of success (4,5)
I believe the answer is:
lost cause
'it has no chance of success' is the definition.
The definition suggests a singular noun which matches the answer.
'terrible lout's case' is the wordplay.
'terrible' indicates an anagram.
'louts'+'case'='loutscase'
'loutscase' anagrammed gives 'LOST CAUSE'.
Can you help me to learn more?
(Other definitions for lost cause that I've seen before include "write-off" , "Hopeless ideal" , "Hopeless case" , "Hopeless endeavour" , "Hopeless situation" .)