Complex sentence: Abbitt also says a large portion of the appeal of Takarazuka comes from something she calls "slippage," referring to the enjoyment derived from a character portraying something they are not, here, a woman portraying a man.
Split into simpler sentences: Abbitt also says a large portion of the appeal of Takarazuka comes from something she calls "slippage". This slippage refers to the enjoyment derived from a character portraying something they are not, in this case a female portraying a man.