Possible Clues:

• Having been shortened, the Spanish died in 7 down
• Shortened to fifty-one, indeed
• Dropped sounds
• Turned nothing into nothin'
• The cover was shortly in it up the river
• Slurred over a syllable
• Dropped a vowel
• One's wont might be this from what one will not
• In short, that's fifty-one, indeed
• Left out vowels