Discharge half of them with it (4)
I believe the answer is:
emit
'discharge' is the definition.
(emitting is a kind of discharging)
'half of them with it' is the wordplay.
'half of' means to take half the letters.
'with' is a charade indicator (letters next to each other).
'them' halved is 'em'.
'em'+'it'='EMIT'
(Other definitions for emit that I've seen before include "'Give out, light say (4)'" , "Broadcast" , "Give off or discharge" , "Give off, gas say" , "Conductor; telegram (US)" .)