Charles broadcast to listeners? (4)
I believe the answer is:
heir
'charles' is the definition.
(Prince Charles is the Queen's heir)
'broadcast to listeners?' is the wordplay.
'broadcast' becomes 'air' (synonyms).
'to listeners?' indicates a 'sounds like' (homophone) clue.
'air' is a homophone of 'HEIR'.
(Other definitions for heir that I've seen before include "One who inherits" , "The first boy maybe" , "Legal successor" , "one's to inherit throne!" , "Acknowledged beneficiary" .)