Way of communicating publicity in city (5)
I believe the answer is:
radio
'way of communicating' is the definition.
'radio' can be an answer for 'communicating' (radio is a kind of communicating). I'm not sure about the 'way of' bit.
'publicity in city' is the wordplay.
'publicity' becomes 'ad' (short for advert).
'in' is an insertion indicator.
'city' becomes 'rio' (Rio de Janeiro).
'ad' inserted inside 'rio' is 'RADIO'.
Can you help me to learn more?
(Other definitions for radio that I've seen before include "Communicate with" , "Receiving device" , "Part of the broadcasting industry" , "send a message" , "Broadcasting medium" .)