。
I don't want to take on any more work than this.
Literal
I [topic-は] this more [of-の] work [topic-は] take-up want-not.
これ以上の仕事 nominalizes これ以上 with の to make 'work beyond this' a noun phrase. 引き受ける ('to undertake, to take on responsibility for') is a compound verb (引く + 受ける = 'pull + receive'). The contrastive は after 仕事 implies 'this kind of work specifically — other things might be fine.'