Rough -- one goes to mush! (5)
I believe the answer is:
husky
I believe this is a double definition.
'rough' is the first definition.
(thesaurus)
'one goes to mush' is the second definition.
(mush can mean a journey with a dog sled)
(Other definitions for husky that I've seen before include "Northern drag performer" , "Muscular" , "Sledge-dog" , "Breed of Arctic dog" , "sounding a little hoarse" .)