pluck at (something)
To grasp and pull or tug at something forcibly and abruptly with one's fingers or a grasping instrument, such as tweezers or pliers. She kept plucking at my sleeve to get my attention. Quit plucking at that thread or you'll ruin the whole sweater.
pluck at someone or something
to pull or pick at someone or something. Kelly plucked at Ed, picking off the burrs that had caught on his clothing. Kelly plucked at the strings of the guitar.