Princess in row over broadcast (5)
I believe the answer is:
radio
'broadcast' is the definition.
(radio broadcast is a kind of broadcast)
'princess in row over' is the wordplay.
'princess' becomes 'di'.
'in' indicates putting letters inside.
'row' becomes 'oar' (oar can mean to row with oars).
'over' says the letters should be written in reverse.
'oar' backwards is 'rao'.
'di' placed into 'rao' is 'RADIO'.
(Other definitions for radio that I've seen before include "Sound broadcasting" , "means of communication" , "Speech receiver" , "It used to be called the wireless" , "Communications receiver" .)