Severe examination: cad set it out (4,4)
I believe the answer is:
acid test
'severe examination' is the definition.
'acid test' can be an answer for 'examination' (I have seen 'Conclusive examination ' mean 'acid test' so perhaps 'examination' could also mean 'acid test'). I'm not certain of the 'severe' bit.
'cad set it out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'cad'+'set'+'it'='cadsetit'
'cadsetit' with letters rearranged gives 'ACID TEST'.
Can you help me to learn more?
(Other definitions for acid test that I've seen before include "'Appraisal to show the true value (4,4)'" , "Conclusive trial of success or value" , "what may prove conclusive" , "Crucial assessment" , "Crucial exam" .)