Severity (6)
'severity' is the definition.
(synonyms)
This is all the clue.
(Other definitions for rigour that I've seen before include "Hardship" , "Strict precision, of thought say" , "Quality of being extremely thorough and careful" , "Excessive severity" , "Trial" .)
'severity' is the definition.
(I know that severity can be written as rigor)
This is all the clue.
(Other definitions for rigor that I've seen before include "Hardship" , "Muscular cramp" , "showing failure to respond" , "Chilled shivering often a symptom of disease" , "Shivering chill before fever" .)