Hammer, anvil and stirrup site (3)
I believe the answer is:
ear
This clue is a double definition.
'hammer' is the first definition.
(thesaurus)
'anvil and stirrup site' is the second definition.
(I've seen this in another clue)
(Other definitions for ear that I've seen before include "Lug (colloq.)" , "Bit of corn" , "Seed container" , "Go astray" , "Listening organ" .)