It's correct to go after loud alarm (6)
I believe the answer is:
fright
'alarm' is the definition.
(I've seen this before)
'it's correct to go after loud' is the wordplay.
'it's correct' becomes 'right' ('right' can be a synonym of 'correct').
'to go after' is a charade indicator (letters next to each other).
'loud' becomes 'f' (A musical term).
'right' put after 'f' is 'FRIGHT'.
(Other definitions for fright that I've seen before include "Terror" , "Sudden exposure to fear" , "Sudden feeling of fear" , "Alarming event" , "Panic" .)