Cutting-edge music, selling well with City hipsters at first (2-4)
I believe the answer is:
hi-tech
'cutting-edge' is the definition.
(at the cutting edge of technology)
'music selling well with city hipsters at first' is the wordplay.
'music selling well' becomes 'hit' (as in a hit song).
'with' is a charade indicator (letters next to each other).
'city' becomes 'EC' (the City of London postcode).
'at first' says to take the initial letters.
The initial letter of 'hipsters' is 'h'.
'hit'+'ec'+'h'='HI-TECH'
(Other definitions for hi-tech that I've seen before include "Electronically advanced" , "Using the latest science" , "(Using) the latest developments" , "Sophisticated electronics" , "Style of interior design using features of industrial equipment" .)