Related Clues:

• Make immune, as to violence (Var.)
• Change to suit a new purpose
• Acclimate
• Adapt to rigors
• Toughen, as to hardship
• Become hardened (to)
• Demonstrate flexibility
• Get used to (Var.)
• Harden: Var.
• Blend in
• Make immune
• Cause to become hardened to
• Make accustomed (to)
• Show elasticity
• Change, evolutionarily