Rather small-minded? That's about right (6)
I believe the answer is:
pretty
'rather' is the definition.
('pretty' can be a synonym of 'rather')
'small-minded? that's about right' is the wordplay.
'small-minded?' becomes 'petty' ('petty' can be a synonym of 'small-minded').
'that's about' is an insertion indicator.
'right' becomes 'r' (common abbreviation).
'petty' enclosing 'r' is 'PRETTY'.
(Other definitions for pretty that I've seen before include "like a kettle of fish" , "See 19" , "Facially attractive" , "Attractive - quite" , "Reasonably" .)