Related Clues:

• Become firm or tough
• Temper, steel say
• Turn to bone with age
• Change into bone, or become unprogressive
• Become hard and bony with age
• Make firm and insensitive
• It's hard to make it like this
• That's just to make it hard
• Strengthen the street if it's over a bog
• Thus one might take 'er in hand to make her tough
• If this fits up over the marsh, that will make more of a firm of it
• This fits up over the marsh so as to make it firm
• If so, Y's able to get hard like this
• It may make it more tough to be a playful forest at last
• At last the playful forest will be the last of 27 across