Possible Clues:

• One-fifth of 'If music be the food of love, play on'
• Metrical short-long foot
• One of 70 in a Shakespearean sonnet
• A two-syllable foot in poetry
• ''But, soft!'', for instance
• Shakespearean fool
• One-fifth of 'Rough winds do shake the darling buds of May'
• Foot, in verse
• You get a foot of this starting just after midnight