Player protecting a QB's blind side, often

LEFTTACKLE

This lineman stands on the quarterback’s left to block defenders coming from behind.

In football, the quarterback's "blind side" is the side they can't see when dropping back to pass, which for right-handed QBs is usually the left. The player responsible for guarding that side is the left tackle, a key offensive lineman who blocks defenders to prevent sacks. The clue hints at this role directly—no wordplay, just a straightforward reference to a critical position in pass protection.