Possible Clues:

• Missed end of planned deadline -- a note omitted here
• Neglected to say, maybe
• Fifty-one shortened, indeed
• Shortened to fifty-one indeed
• Skipped a phoneme
• 'With cover in the river up there, it's been shortened, in a manner of speaking (6)'
• Said 'bos'n' for 'boatswain,' e.g.
• Ran together, in a manner of speaking
• Made short of the cover in the Dee up there
• Fifty-one, indeed, has got compressed