Location of the islets of Langerhans (8)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
pancreas
(Other definitions for pancreas that I've seen before include "organ" , "Large gland behind the stomach" , "Gland near stomach discharging insulin" , "Gland aiding digestion" , "Gland near stomach, sends insulin into blood" .)