Thanks murky for helping the pennies (x2) to drop with regard to the last clue. However, the two unclued answers are still as clear as mud. (There are three possible fourth letters for the shorter one: E, O, U.)
xij, the first in Group 3 requires a three-letter word for worry, one of which is redundant, then alternate letters of a later word in the clue, the 'bars' in the def being musical. The fourth in Group 1 is one I had trouble with, but IS + TT should help, and the poet is unambiguous, although I can't parse the first four words.