Dispatch mostly words on passing data unit (7)
I believe the answer is:
kilobit
'passing data unit' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'dispatch mostly words' is the wordplay.
'dispatch' becomes 'kill' (I've seen this before).
'mostly' means to remove the last letter.
'words' becomes 'obit' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'kill' with its last letter removed is 'kil'.
'kil'+'obit'='KILOBIT'
'on' is the link.
Can you help me to learn more?
(Another definition for kilobit that I've seen is " (In computing) a unit of information".)