Publication's first Listener advertisement (4)
I believe the answer is:
plug
'advertisement' is the definition.
(thesaurus)
'publication's first listener' is the wordplay.
'first' says to take the initial letters.
'listener' becomes 'lug' (informal Scottish term for a person's ear**).
The first letter of 'publications' is 'p'.
'p'+'lug'='PLUG'
(Other definitions for plug that I've seen before include "Blatant promotion" , "Mention favourably - stopper" , "quid" , "Bath or sink stopper" , "Stop - advertising" .)