Mojo

Her mojo was among the things that Clara Oswald lost as a child. She eventually got it back. (WC: The Bells of Saint John: A Prequel)

Behind the scenes
While the exact meaning of "mojo" was not specified in the episode, Clara was most likely using mojo as slang. To have "lost your mojo" refers to a loss of inspiration or creative genius, the loss of that special spark.

However, mojo could also refer to the magazine, a music magazine that has been published in the UK since 1993. Mojo can be also be a reference to charm or sex drive, a meaning heavily popularised by the series. Since the Austin Powers films were released during Clara's childhood, she may very well have been aware of them when she made this reference.