Study concerning publicity (4)
I believe the answer is:
read
'study' is the definition.
(I know that study can be written as read)
'concerning publicity' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'publicity' becomes 'ad' (short for advert).
're'+'ad'='READ'
(Other definitions for read that I've seen before include "Speak" , "See - peruse - understand" , "(Of passage) have a certain wording" , "Perused" , "Study (for a degree?)" .)