A record capturing French horn concert (6)
I believe the answer is:
accord
'concert' is the definition.
(I've seen this in another clue)
'a record capturing french horn' is the wordplay.
'record' becomes 'CD' (compact disc).
'capturing' means one lot of letters goes inside another.
'french horn' becomes 'cor' ('horn' in French).
'cd' placed around 'cor' is 'ccord'.
'a'+'ccord'='ACCORD'
(Other definitions for accord that I've seen before include "'Agreement, treaty (6)'" , "Myra -, pianist; Rudolf -, Nazi" , "Correspond" , "Official treaty" , "Be in harmony or consistent" .)