Possible Clues:

• How 30 across gets about five hundred to wait on you, perhaps
• At last one is sinewy in weight
• Tissue attaching muscle to bone
• At last it's in a lot of weight to make SI new, perhaps
• That would be apt to get on in you
• Ligament - sinew
• Strong tissue that connects muscle
• Academic figure leading to link with Achilles?
• It takes sinew to finish in weight like this
• In words