It was a wrench to hear that his best friend was moving to another country.

wrench 的本义是"扳手"，指用来拧紧或松开螺母的工具。在这里用作比喻意义，表示"突然的分离或痛苦"，就像用扳手拧动时产生的强烈不适感，形容听到朋友离开消息时内心的痛苦和失落。