扣住頸項 Tethered By The Neck
即解下勒袍腰帶，把鹿扣住頸項，牽將起來，道：「大聖，我和你比丘國相見去也。」行者道：「且住，索性把這邊都掃個乾淨，庶免他年復生妖孽。」即解下勒袍腰带，把鹿扣住颈项，牵将起来，道：「大圣，我和你比丘国相见去也。」行者道：「且住，索性把这边都扫个干净，庶免他年复生妖孽。」
逐句解 Line by line
He undid the sash from his gown, buckled it round the deer's neck, pulled it up and said, "Great Sage, you and I will go to the kingdom of Bhikṣu and be seen."
勒袍腰帶 is the sash that gathers a Daoist's robe. The god takes off his own belt to make a halter — an improvised tether, and the last stage of turning the Royal Father-in-Law back into livestock. 牽將起來, hauled up onto its feet by it.
Pilgrim said, "Wait a moment. We may as well sweep this place clean while we are here, so as to spare it another crop of fiends in years to come."
索性 — might as well, and be done with it — is still exactly the modern word. 庶免他年復生妖孽 is Wukong thinking about the future of a place he has no connection to. He is nine tenths of the way through the job and stops to consider what grows back. 乾 is gān in 乾淨, dry-and-clean — not the qián of the trigram.
The tether is the chapter's plainest image of what has happened. A creature that held a kingdom by the throat for three years leaves it on the end of an old man's belt.
Wukong's afterthought is the same instinct that produced "cut off the trouble at the root" — an idea the king, the palace women and now he himself have all reached for. He is the only one of the three about to do anything about it.