Answer: To perform magic
Step-by-step explanation:
The phrase is: 'Perhaps he was shouting - but the sound did not reach me. But how the deuce had he done this? I felt like a man who has just seen a new conjuring trick.'
In this context, the word conjuring refers to performing some kind of magic trick, because the speaker uses it as a metaphor of something unexplainable at first sight. It doesn´t refer to the action of calling someone, nor bringing something to mind. Although the word 'conjuring might usually be used to refer to the summons of a spirit, in this sentence that wouldn´t make sense.