Possible Clues:

• Toughen or harden
• Temper is not usually raised except initially
• Harden, habituate
• Get used to conditions in river
• How to get hardened to having R there?
• Harden or season
• Harden or accustom as to something unpleasant
• Harden against, make tough
• Accustom, harden (to)
• That will get one used to the ruin over the East