Lussurioso, the Duke's heir by his first marriage, has asked him if he can find a procurer to obtain a young virgin he lusts after; the brothers decide that Vindice will undertake this role in disguise, to give an opportunity for their revenge.
He lusts after. This was what Lussurioso has asked him. He can find a procurer to obtain a young virgin. Lussurioso is the Duke's heir by his first marriage. Vindice will undertake this role in disguise. This is to give an opportunity for their revenge. The brothers decide this.