Sentence:  For London to have its own exclusive immigration policy would exacerbate the sense that immigration benefits only certain groups and disadvantages the rest. It would <WSD>entrench</WSD> the gap between London and the rest of the nation. And it would widen the breach between the public and the elite that has helped fuel anti-immigrant hostility. 
Meaning of the word marked with <WSD> tags:  To establish a substantial position in business, politics, etc.