  Aims. We investigate the configuration of a complex flux rope above a
{\delta} sunspot region in NOAA AR 11515, and its eruptive expansion during a
confined M5.3-class flare.
  Methods. We study the formation of the {\delta} sunspot using continuum
intensity images and photospheric vector magnetograms provided by SDO/HMI. We
use EUV and UV images provided by SDO/AIA, and hard X-ray emission recorded by
RHESSI to investigate the eruptive details. The coronal magnetic field is
extrapolated with a non-linear force free field (NLFFF) method, based on which
the flux rope is identified by calculating the twist number Tw and squashing
factor Q. We search the null point via a modified Powell hybrid method.
  Results. The collision between two emerging spot groups form the {\delta}
sunspot. A bald patch (BP) forms at the collision location, above which a
complex flux rope is identified. The flux rope has multiple layers, with one
compact end and one bifurcated end, having Tw decreasing from the core to the
boundary. A null point is located above the flux rope. The eruptive process
consists of precursor flaring at a 'v'-shaped coronal structure, rise of the
filament, and flaring below the filament, corresponding well with the NLFFF
topological structures, including the null point and the flux rope with BP and
hyperbolic flux tube (HFT). Two sets of post-flare loops and three flare
ribbons support the bifurcation configuration of the flux rope.
  Conclusions. The precursor reconnection, which occurs at the null point,
weakens the overlying confinement to allow the flux rope to rise, fitting the
breakout model. The main phase reconnection, which may occur at the BP or HFT,
facilitates the flux rope rising. The results suggest that the {\delta} spot
configuration presents an environment prone to the formation of complex
magnetic configurations which will work together to produce activities.
