West Side Story gang (4)
I believe the answer is:
jets
'west side story gang' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for jets that I've seen before include "Rapid streams of liquid or gas" , "Aeroplanes - Sharks rivals in "West Side Story"" , "Water spouts or fast planes" , "Fast airplanes" .)