US city series to make you beam (5)
I believe the answer is:
laser
'beam' is the definition.
(laser beam is a kind of beam)
'us city series' is the wordplay.
'us city' becomes 'LA' (Los Angeles).
'series' becomes 'ser' (abbreviation for series).
'la'+'ser'='LASER'
'to make you' acts as a link.
(Other definitions for laser that I've seen before include "Optical device producing an intense beam of light" , "Device producing a narrow, intense beam of light" , "E.g. surgical light-beam" , "Device producing thin beam of light" , "Device yielding powerful beam" .)