Crossword puzzle clue "what the circled parts of this puzzle comprise"

What the circled parts of this puzzle comprise

Former UN leader Hammarskjöld [Note: The circled letters comprise a three-word instruction that, when applied to one square in the completed grid, reveals a group who might follow a code of silence]

Like the squares that comprise this puzzle's special letters

Fashion runway, or, in a way, what this puzzle's 10 perimeter answers comprise

Legislation signed 6/22/1944 by FDR ... and, initially, what the nine longest across answers in this puzzle comprise

School's underclass team ... or, initially, what the four longest answers in this puzzle comprise

Moves like a buoy in the ocean ... or a hint to the circled parts of this puzzle?

Poet whose classic work is hidden in this puzzle (see the circled squares of the completed the puzzle)