Thyroid for instance (5)
I believe the answer is:
gland
'thyroid for instance' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gland that I've seen before include "it could be described as secretive" , "Organ that secretes" , "Organ that separates substances from blood" , "liver, for example" , "Organ secreting chemical substances" .)