Accustomed (to) (6)
(Another definition for enured that I've seen is " toughened up".)
'accustomed to' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for inured that I've seen before include "Accustomed to something difficult" , "Hardened, maybe ruined" , "Hardened, accustomed" , "used to it" , "Hardened against, emotion say" .)