Cast off top of silo — see, it’s disgusting (6)
I believe the answer is:
slough
'cast off' is the definition.
(sloughing is a kind of casting off)
'top of silo see it's disgusting' is the wordplay.
'top of' suggests taking the first letters.
'see' becomes 'lo' (archaic word meaning 'look!').
'it's disgusting' becomes 'ugh' (I've seen this before).
The initial letter of 'silo' is 's'.
's'+'lo'+'ugh'='SLOUGH'
(Other definitions for slough that I've seen before include "Swamp; Berkshire town" , "Swamp; cast off (skin)" , "Berkshire town - bog - shed" , "poet wanted destroyed" , "Swamp; shed (dead skin)" .)