Fairly? I should say so (6)
I believe the answer is:
I believe this is a double definition.
'fairly?' is the first definition.
(I've seen this before)
'i should say so' is the second definition.
(both are expressions used to show agreement)
(Other definitions for rather that I've seen before include "Yes, please!" , "On the contrary; sooner" , "On the contrary or to some extent" , "More precisely; instead of" , "Most certainly" .)