Charming bore? Not exactly (6,4)
I believe the answer is:
pretty well
'not exactly' is the definition.
I can't judge whether this defines the answer.
'charming bore?' is the wordplay.
'charming' becomes 'pretty' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'bore?' becomes 'well' (I've seen this before).
'pretty'+'well'='PRETTY WELL'
Can you help me to learn more?
(Other definitions for pretty well that I've seen before include "More or less" , "Practically" , "Aim of dressing in Derbyshire" , "Close to" , "Sort of" .)