Possible Clues:

• One's wont might be this from what one will not
• With a bit cut out, died at last all twisted
• Just over fifty gets left out in one of 15 across
• Cover in back river cut off
• Dropped (e.g. vowel)
• Omitted in speaking
• That's just over half a century shortened, indeed
• Left a bit out and put fifty-one in, indeed
• Indeed, just over fifty ran together
• Having been shortened, the Spanish died in 7 down