Section of bar that's about right (7)
I believe the answer is:
excerpt
'section' is the definition.
(excerpt is a kind of section)
'bar that's about right' is the wordplay.
'bar' becomes 'except' (both can mean 'not including').
'that's about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'except' enclosing 'r' is 'EXCERPT'.
'of' is the link.
(Other definitions for excerpt that I've seen before include "part of article, perhaps" , "A passage from, music or book" , "Selected passage from larger work" , "1D [CLIP]" , "Textual passage" .)