Quiet, cultured person (5)
I believe the answer is:
party
'person' is the definition.
(eg an individual in a court case)
'quiet cultured' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'cultured' becomes 'arty' (I've seen this in another clue).
'p'+'arty'='PARTY'
(Other definitions for party that I've seen before include "Political organization" , "Political organisation" , "MP's faction" , "See 22" , "push the boat out" .)