Loud American ship creating bother (4)
I believe the answer is:
fuss
'bother' is the definition.
(I know that bother can be written as fuss)
'loud american ship' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'american ship' becomes 'USS' (United States Ship, prefix used in US ship names).
'f'+'uss'='FUSS'
'creating' is the link.
(Other definitions for fuss that I've seen before include "trouble" , "Bustle; ado" , "Bustle and bother" , "Display of unnecessary interest" , "(Show) excessive concern" .)