A bit roughly, I beg your pardon (8)
I believe the answer is:
somewhat
'a bit' is the definition.
(I've seen this before)
'roughly i beg your pardon' is the wordplay.
'roughly' becomes 'some' ('some' can be a synonym of 'roughly').
'i beg your pardon' becomes 'what' (I've seen this before).
'some'+'what'='SOMEWHAT'
(Other definitions for somewhat that I've seen before include "Moderately" , "Rather, a little" , "up to a point" , "To a moderate extent" , "To an extent, a little" .)