Brushing off one good impediment to marriage proposal? (8)
I believe the answer is:
ignoring
'brushing off' is the definition.
('ignore' can be a synonym of 'brush off')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for ignoring that I've seen before include "Refusing to acknowledge" , "Paying no attention to" , "Refusing to notice" .)