It's tough, making a hash outright! (5)
I believe the answer is:
harsh
'it's tough' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for harsh that I've seen before include "Grating; severe" , "Severe - unkind" , "Strident" , "Unkind or cruel" , "Jarring" .)