Hit sung loudly after dropping out (6)
I believe the answer is:
belted
'hit' is the definition.
'sung loudly after dropping out' is the wordplay.
'sung loudly' becomes 'belted out' ('belt out' can be a synonym of 'sing loudly').
'after dropping' indicates named letters should be taken away.
'beltedout' with 'out' taken away is 'BELTED'.
(Other definitions for belted that I've seen before include "as an earl may be" , "beaten" , "whacked" , "Ran furiously" , "Dealt a heavy blow" .)