Preferably pretty (6)
I believe the answer is:
rather
I believe this is a double definition.
'preferably' is the first definition.
('rather' can be a synonym of 'preferably')
'pretty' is the second definition.
('rather' can be a synonym of 'pretty')
(Other definitions for rather that I've seen before include "Infinite time" , "Somewhat; more willingly" , "On the contrary; more precisely" , "A bit" , "Quite; on the contrary" .)