Charity provided by the heartless alarms (4)
I believe the answer is:
alms
'charity' is the definition.
(alms is a kind of charity)
'the heartless alarms' is the wordplay.
'the heartless' means to remove the middle letters.
'alarms' with its centre removed is 'ALMS'.
'provided by' acts as a link.
(Other definitions for alms that I've seen before include "Charitable donations to poor" , "help" , "Charitable relief" , "Charitable donations to the needy" , "Charitable gifts - slam them" .)