She has less of a role than some of the other repeat characters, but Clara makes an impact. We know Doc well; any woman he would love needs to impress us.
In order to match with Doc, she has to be a science nerd, and she is. It goes beyond a love of Jules Verne, though. Her telescope has an entire backstory, and she has a lifelong relationship with science. Well done.
She’s obviously brave. A lone woman schoolteacher sets off into the Wild West, arriving by train in a town where she knows no one. It’s easy to forget how risky such a move would be back then.
A practical woman who dares to adventure? Seven. It’s her clinical reactions that define her Enneagram. Doc breaks her heart, she’s leaving. New information tells her Doc loves her, she’s returning. Doc has a model train set with a piece labeled “time machine”, she believes him. Doc’s off to travel through time, she follows. She just does the next thing in front of her, no matter how unrealistic and ludicrous. That willingness is very Seven.