Familiar voice replied initially: "farewell Jack" (5,4)
I believe the answer is:
radio star
'familiar voice' is the definition.
The definition suggests a singular noun which matches the answer.
'replied initially farewell jack' is the wordplay.
'initially' says to take the initial letters.
'farewell' becomes 'adios' (adios is a kind of farewell).
'jack' becomes 'tar' (both are informal terms for sailor).
The initial letter of 'replied' is 'r'.
'r'+'adios'+'tar'='RADIO STAR'
Can you help me to learn more?
(Other definitions for radio star that I've seen before include "Sky feature" , "Important broadcaster" .)