Modernise a quiet duet perhaps (6)
I believe the answer is:
update
'modernise' is the definition.
(I've seen this before)
'a quiet duet perhaps' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'perhaps' indicates anagramming the letters.
'a'+'p'+'duet'='apduet'
'apduet' is an anagram of 'UPDATE'.
(Other definitions for update that I've seen before include "Bring to the latest state, records say" , "Bulletin" , "Modernise, modify" , "Revise to include latest developments" , "Latest information" .)