By taking a piano concerto extract (3)
I believe the answer is:
per
'by' is the definition.
(I've seen this in another clue)
'a piano concerto extract' is the wordplay.
'a piano' becomes 'p' (musical abbreviation).
'concerto extract' becomes 'er' (I can't justify this - if you can you should give a lot more credence to this answer).
'p'+'er'='PER'
'taking' acts as a link.
Can you help me to learn more?
(Other definitions for per that I've seen before include "Preposition indicating by means of" , "Preposition meaning for each" , "For each or every" , "According to" .)