Bobby, a well-known conductor (6)
I believe the answer is:
copper
'well-known conductor' is the definition.
'copper' can be an answer for 'conductor' (copper is a kind of conductor). I am not certain of the 'well-known' bit.
'bobby a' is the wordplay.
'bobby' becomes 'cop' (I've seen this in other clues).
'a' becomes 'per' (eg 'one a day' means 'one per day').
'cop'+'per'='COPPER'
Can you help me to learn more?
(Other definitions for copper that I've seen before include "Metal - wash basin" , "bluebottle" , "Metallic element for a British policeman" , "Old policeman or reddish metal" , "Metal, Cu" .)