It's in the neck or back. That's about it! (6)
I believe the answer is:
throat
'it's in the neck' is the definition.
I can't tell whether this defines the answer.
'or back that's about it' is the wordplay.
'back' shows that the letters should be reversed in order.
'about it' is an insertion indicator (some letters go around or about others).
'or' backwards is 'ro'.
'ro' inserted inside 'that' is 'THROAT'.
Can you help me to learn more?
(Other definitions for throat that I've seen before include "site for swallows" , "Top part of the windpipe" , "Narrow entrance" , "Front part of the neck" , "Hot tar (anag.)" .)