Long used and possibly ruined (6)
I believe the answer is:
inured
'long used' is the definition.
Although both the answer and definition are past participle verbs, I don't see how one could define the other.
'possibly ruined' is the wordplay.
'possibly' is an anagram indicator.
'ruined' anagrammed gives 'INURED'.
'and' is the link.
Can you help me to learn more?
(Other definitions for inured that I've seen before include "Hardened, maybe ruined" , "Hardened, accustomed" , "Hardened against, toughened" , "Habituated or hardened" , "Hardened as by experience" .)