Light chatter with city politician (3,4)
I believe the answer is:
gas lamp
'light' is the definition.
(gas lamp is a kind of light)
'chatter with city politician' is the wordplay.
'chatter' becomes 'gas' (I've seen this before).
'with' means one lot of letters go next to another.
'city' becomes 'LA' (Los Angeles).
'politician' becomes 'MP' (Member of Parliament).
'gas'+'la'+'mp'='GAS-LAMP'
(Other definitions for gas lamp that I've seen before include "may be illuminating" , "Sort of light" , "Bright object" , "Victorian street light" , "Old illuminator" .)