Satellite telephone, brilliant (7)
I believe the answer is:
telstar
'satellite' is the definition.
(US satellite programme)
'telephone brilliant' is the wordplay.
'telephone' becomes 'tel' (short for telephone).
'brilliant' becomes 'star' (star can mean brilliant eg star performer).
'tel'+'star'='TELSTAR'
(Other definitions for telstar that I've seen before include "Old satellite" , "Communications satellite" , "Communication satellite" , "Early sixties satellite" , "Distant transmitter" .)