Understands broadcast - fiddle with electronic part of rocket (4,4)
I believe the answer is:
nose cone
'part of rocket' is the definition.
(I know that nose cone is part of rocket)
'understands broadcast fiddle with electronic' is the wordplay.
'understands' becomes 'knows' (understand can mean to know or recognise).
'broadcast' shows a homophone (sound like) (how the word might sound on the radio or TV).
'fiddle' becomes 'con' (both can mean a scam).
'with' is a charade indicator (letters next to each other).
'electronic' becomes 'e' (as in e-mail or e-books).
'knows' sounds like 'nose'.
'nose'+'con'+'e'='NOSE-CONE'
(Other definitions for nose cone that I've seen before include "Part of aircraft" , "Front of rocket" , "Front part of a spacecraft, etc" , "part of missile" , "Challenger at the front" .)