。
That company demands a high level of specialized expertise.
Literal
That company [at-では] high specialty [subj-が] is-required [polite-される].
~では (で + は) here contrastively sets 'that company' as the location/domain where the requirement applies. 専門性 'specialty / specialized expertise' uses the ~性 suffix to turn 専門 'specialty' into an abstract quality noun. 要求される is the passive of 要求する 'to demand,' with the agent (the company, implicitly) demoted. The whole sentence typifies formal descriptive writing about workplaces.