Gauging just how bad the reprimand was? (6)
I believe the answer is:
rating
'gauging' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rating that I've seen before include "Doing an appraisal" , "Non-commissioned sailor - classification" , "Sailor - assessment" , "Score" , "Classification assigned to person as, say, for income" .)