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 defines the answer.
'possibly last' is the wordplay.
'possibly' is an anagram indicator.
'last' anagrammed gives '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" .)