Eg, liver or heart (5)
I believe the answer is:
organ
This clue is a double definition.
'eg liver' is the first definition.
(I know that liver is a type of internal organ)
'heart' is the second definition.
(the heart is an example)
(Other definitions for organ that I've seen before include "Soft part of the body which has a specific function" , "Instrument - heart, for example" , "Musical instrument - pancreas, perhaps" , "Eg, heart, liver" , "Part with special function" .)