Sentence:  When Timothy and Julia hurried up the staircase to the bedroom floor, where a considerable commotion was taking place, Tim took Barry Leach with him. He had him gripped <WSD>firmly</WSD> by the arm, since he felt it was not safe to let him loose, and he had no immediate idea what to do with him. 
Meaning of the word marked with <WSD> tags:  Securely.