Jam with loud music in a bad way (4)
I believe the answer is:
fill
'jam' is the definition.
('fill' can be a synonym of 'jam')
'with loud music in a bad way' is the wordplay.
'with' means one lot of letters go next to another.
'loud music' becomes 'f' (forte - musical term meaning loud).
'in a bad way' becomes 'ill' (I've seen this before).
'f' put next to 'ill' is 'FILL'.
(Other definitions for fill that I've seen before include "Block up (a hole, etc)" , "Repair tooth" , "Plug (a gap)" , "Appoint person to (post)" , "` `Work expands to .... the time available' '" .)