THE CLOUD OF UNKNOWING - CHAPTER 66
"The other secondary power, which is called sensuality; its activity and its obedience to the will, before and after original sin."
The quoted chapter heading is from the Paulist Press edition. In this chapter we read that since the fall, sensuality is no longer obedient to the will, "unless ruled by grace in the will." Thus, sensuality is what keeps us distracted from spiritual things by the attractions of the flesh, and the unattractiveness of spiritual things to the sensual power of our mind.
As we monitor our mental and spiritual activities, in the practice of this exercise, to see whether our minds are on things below us, or on beings equal to us, or on God, our author is pointing out that sometimes it is these secondary powers of the mind which cause our thoughts to not be on God.