Over in Big Bash final for Mitch Marsh (6)
I believe the answer is:
slough
'marsh' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for slough that I've seen before include "Swamp or marshy place, maybe of despond" , "shed covering" , "Swamp; cast off (skin)" , "Discard - bog" , "Swamp; Berkshire town" .)