Possibly last to go through the mill? (4)
I believe the answer is:
salt
'go through the mill?' is the definition.
I can't judge whether this definition defines the answer.
'possibly last' is the wordplay.
'possibly' indicates an anagram.
'last' is an anagram of 'SALT'.
'to' is the link.
Can you help me to learn more?
(Other definitions for salt that I've seen before include "Pile up" , "A defence against ice" , "Seasoned sailor" , "Mariner; sodium chloride" , "NaCl" .)