Broadcast Martin's arranged on time (8)
I believe the answer is:
transmit
'broadcast' is the definition.
('transmit' can be a synonym of 'broadcast')
'martin's arranged on time' is the wordplay.
'arranged' indicates anagramming the letters.
'on' means one lot of letters go next to another.
'time' becomes 't' (**).
'martins' with letters rearranged gives 'ransmit'.
'ransmit' put after 't' is 'TRANSMIT'.
(Other definitions for transmit that I've seen before include "Pass or hand on" , "Send from one to another, electronically say" , "Send - communicate" , "Communicate (an idea)" , "Send from one person to another, or broadcast" .)