Quiet argument on the ship (4)
I believe the answer is:
prow
'the ship' is the definition.
(thesaurus)
'quiet argument on' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano').
'argument' becomes 'row' (I've seen this before).
'on' means one lot of letters go next to another.
'p'+'row'='PROW'
(Other definitions for prow that I've seen before include "Pointed front part of a vessel" , "Boat's bow" , "Bow of a vessel" , "Front end of ship" , "Projecting front part of ship" .)