The top part of the windpipe (6)
I believe the answer is:
throat
'the top part of the windpipe' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for throat that I've seen before include "It's inside the neck" , "Front part of the neck" , "Passage from the back of the mouth" , "end of gaff" , "A frog is a problem in this" .)