Possible Clues:

• Sylvester seems able to put a word together
• Single sounded unit of a word
• One has one of them, and seven two
• See 20
• One of two in seven
• Sly plan to get fit after losing lead? In a word, that's part of what's been said!
• Sounding part of a word
• One of 14 in 'supercalifragilisticexpialidocious'
• Stretch your legs largely on summits of Italian island going up for a bit of a word
• Sneak's just one -- but there's another in cahoots and a third in custody