Note competent guy (5)
I believe the answer is:
cable
'guy' is the definition.
(I've seen this in other clues)
'note competent' is the wordplay.
'note' becomes 'c' (musical note).
'competent' becomes 'able' (similar in meaning).
'c'+'able'='CABLE'
(Other definitions for cable that I've seen before include "This may pull car up" , "Thick wire; telegram" , "Anchor chain; type of TV" , "Strong line" , "Naut. length; transmit" .)