Possible Clues:

• T's frequency?
• Quite frequently, according to the poet
• Frequently ring -- daily, in short
• Perhaps T's in the chilly night
• Old song'... in the stilly night'
• Met Al with a letter at last in a hundred more
• Many a time poetically speaking, Oscar joins paper
• Commonly, once
• (Poetically) frequently
• Frequently, to an Old English lyricist