Sentence:  He concluded very naturally that the boy had come to some crisis in his unfortunate entanglement with Madeleine Philips, and he was flattered by the trustfulness that brought the matter to him. He resolved to be delicate but wily, honourable, strictly honourable, but steadily, patiently <WSD>separative</WSD>. 
Meaning of the word marked with <WSD> tags:  Serving to separate.