Shed somewhere in Berkshire (6)
I believe the answer is:
I believe this clue is a double definition.
'shed' is the first definition.
(both can mean to cast off)
'somewhere in berkshire' is the second definition.
(town in Berkshire)
(Other definitions for slough that I've seen before include "Swamp; shed (dead skin)", "A bog or marsh, perhaps of despond", "Swamp; cast off (skin)", "Berkshire town - bog - shed", "poet wanted destroyed".)