Safety-first objective in broadcast (4)
I believe the answer is:
send
'broadcast' is the definition.
('send' can be a synonym of 'broadcast')
'safety-first objective' is the wordplay.
'first' suggests taking the first letters.
'objective' becomes 'end' (I've seen this before).
The initial letter of 'safety' is 's'.
's'+'end'='SEND'
'in' is the link.
(Other definitions for send that I've seen before include "Mail" , "Despatch, remit" , "Forward" , "Consign" , "Transport" .)