grasp at (someone or something)
To attempt to hold onto or grip someone or something. I grasped at the dog, but she ran away from me. Liz and I grasped at the sides of the raft as we hit rough waters.
grasp at someone or something
to try to seize someone or something. He grasped at the bar and held on tight. The beggar grasped at the pedestrian and lost his grip.
To have a hold on something or take hold of something with the hands: Afraid of the steep drop-off, I grasped at the railing.