Quite a bit! (6)
I believe the answer is:
rather
This clue is a double definition.
'quite' is the first definition.
('rather' can be a synonym of 'quite')
'a bit' is the second definition.
(I have seen 'A bit' mean 'rather' so perhaps 'bit' could also mean 'rather')
(Other definitions for rather that I've seen before include "On the contrary; more precisely" , "Slightly, more so than not (6" , "Quite, sort of" , "On the contrary; sooner" , "Somewhat; more willingly" .)