Possible Clues:

• One of a bird's waterproof covering
• Sire acquiring energy — with 9 + 4 is nominally said to be 21 6
• Arrow part made from an iron-earth mix
• Terror around the structure of a wing
• Quill from magpie’s tail held by old man
• Birds of a ... flock together
• Phobia about the quill
• Element of plumage ... and a feature shared by every answer crossing this one
• Achievement by that woman is something insignificant
• Lightly touch on that woman's achievement first