The phrase "to shield the ball" means to use your body to block or protect the ball from opponents so they can't take it away from you. Full definition
He has to play it simple when in defensive situation or shield the ball better. (justarsenal.com)
And big players have no special natural advantage in shielding a ball and holding off a defender etc — YaYa Toure is good at this but because he has ability not because he is physically intimidating. (justarsenal.com)
Two minutes later, he finally received a foul call after being hacked four times while shielding the ball from the Dallas defenders. (sounderatheart.com)