Bar about right for selected passage (7)
I believe the answer is:
excerpt
'selected passage' is the definition.
(I've seen this in another clue)
'bar about right for' is the wordplay.
'bar' becomes 'except' (both can mean 'not including').
'about' indicates putting letters inside.
'right for' becomes 'r' (I can't justify this - if you can you should believe this answer much more).
'except' going around 'r' is 'EXCERPT'.
Can you help me to learn more?
(Other definitions for excerpt that I've seen before include "Passage taken from book etc" , "newspaper clipping" , "Quote" , "Piece of work" , "Literary section" .)