Sentence:  Wendy thought that her therapist was looking down her <WSD>cleavage</WSD> and said so. The therapist was mortified and chiefly felt guilty, unsure whether she had been looking down her patient's <WSD>cleavage</WSD> or not. On a reflex she assured Wendy that she was not looking down her <WSD>cleavage</WSD> and the matter appeared to rest. 
Meaning of the word marked with <WSD> tags:  The hollow or separation between a woman's breasts, especially as revealed by a low neckline. (from 20th c.)