Thats part of the fuselage and early GR.1s did not have flares.
You can see by the photos of the Sidewinder trials in Germany flares were not mounted.
This is a SEPECAT Jaguar International. An different variant of the aircraft.
As I have already explained, we have a GR.1 with its correct sidewinder mounting. Overwing Pylons, later engines and the later upgrades will come in a future variant (GR.1A).