  In this article, we investigate the formation and disruption of a coronal
sigmoid from the active region (AR) NOAA 11909 on 07 December 2013, by
analyzing multi-wavelength and multi-instrument observations. Our analysis
suggests that the formation of `transient' sigmoid initiated $\approx$1 hour
before its eruption through a coupling between two twisted coronal loop
systems. A comparison between coronal and photospheric images suggests that the
coronal sigmoid was formed over a simple $\beta$-type AR which also possessed
dispersed magnetic field structure in the photosphere. The line-of-sight
photospheric magnetograms also reveal moving magnetic features, small-scale
flux cancellation events near the PIL, and overall flux cancellation during the
extended pre-eruption phase which suggest the role of tether-cutting
reconnection toward the build-up of the flux rope. The disruption of the
sigmoid proceeded with a two-ribbon eruptive M1.2 flare (SOL2013-12-07T07:29).
In radio frequencies, we observe type III and type II bursts in meter
wavelengths during the impulsive phase of the flare. The successful eruption of
the flux rope leads to a fast coronal mass ejection (with a linear speed of
$\approx$1085 km s -1 ) in SOHO/LASCO field-of-view. During the evolution of
the flare, we clearly observe typical "sigmoid-to-arcade" transformation. Prior
to the onset of the impulsive phase of the flare, flux rope undergoes a slow
rise ($\approx$15 km s -1 ) which subsequently transitions into a fast eruption
($\approx$110 km s -1 ). The two-phase evolution of the flux rope shows
temporal associations with the soft X-ray precursor and impulsive phase
emissions of the M-class flare, respectively, thus pointing toward a feedback
relationship between magnetic reconnection and early CME dynamics.
