Driver
noun
You know that 運転 has to do with driving, right? And you know that 手 often has to do with a person doing something in words like these. So, a person who does driving is what? A driver.
うんてんしゅ
The reading is all on'yomi, because it's jukugo. You should know the on'yomi reading of 手 by now just by seeing similar word patterns to this one.
タクシーに乗ったら運転手がトーフグのコウイチだった。
When I took the taxi, the driver happened to be Tofugu's Koichi.
バスの運転手と言い争いになってしまった。
I ended up getting in an argument with the bus driver.
運転手は大丈夫だったみたいだけど、車は事故でめちゃくちゃになっていたよ。
The driver seemed okay but his car was totaled in the accident.