Concert's opening with proficient conductor (5)
I believe the answer is:
cable
'conductor' is the definition.
(I know that cable is a type of conductor)
'concert's opening with proficient' is the wordplay.
'opening' suggests taking the first letters.
'with' is a charade indicator (letters next to each other).
'proficient' becomes 'able' (able can mean capable or proficient).
The initial letter of 'concerts' is 'c'.
'c'+'able'='CABLE'
(Other definitions for cable that I've seen before include "Anchor chain; type of TV" , "Thick wire; telegram" , "Satellite alternative?" , "Strong line" , "Strong thick rope made of twisted hemp or steel wire" .)