Nothing to add to concert advertisement (5)
I believe the answer is:
promo
'advertisement' is the definition.
(short for promotion)
'nothing to add to concert' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'to add to' is a charade indicator (letters next to each other).
'concert' becomes 'prom' (abbreviation for promenade concert).
'o' put after 'prom' is 'PROMO'.
(Other definitions for promo that I've seen before include "Ad" , "advertisement" , "Publicity for project or product (abbr)" , "Advertising film or video" , "Brief publicity" .)