A word from IT to be effective when spoken (4)
I believe the answer is:
byte
'a word from it' is the definition.
(group of computer bits)
'be effective when spoken' is the wordplay.
'be effective' becomes 'bite' (to bite is to have an effect).
'when spoken' shows a homophone (sound like).
'bite' sounds like 'BYTE'.
'to' is the link.
(Other definitions for byte that I've seen before include "quantity of information" , "Unit of computer memory size" , "Computer space storage unit" , "Computer's unit of stored memory" , "Several bits of information" .)